Ok so 1st off this is going to be a very long list of things I've done and had done(in order) prior to getting to the issue at hand. I bought a black 1995 2 Door 4x4 Automatic 4.3L CPI with 158K on it in 2008.
After having the truck for a few months to a year (less than 2000k had been put on it) the high pressure oil line blew one day and I had it replaced, after I got it back there was appearnelty worse damage than I thought because the truck began to knock.

-October 2009 I spun my altinator bearing playing off road and replaced it and the serpentine belt(160k)
-As the knock got worse with time I started using 50 weight oil, eventually this took its toll on the flexplate teeth in the winter of 2009-2010 so I had that replaced
-Feb 2010 D-day came and the engine finially blew, over the time I was saving up to buy a new engine for it. I got a 4.3L CPI (top mounted dist prongs) with 135k on it, engine compression tested good ( I beleive it came from a 94 Olds Bravrada)
-Engine was replaced March 2010, to help my save money most of the old parts from my engine were reused (plugs wires, coils, sensors, dist, etc) everything ran great for months untill one day out of the blue the it idled rough and cut off at a stop light and would not cut back on that night or the next day. Anyway got it towed only to find out it was an ignition coil wire(yeah that sucks tell me about it)
-Summer 2010 replaced the ignition coil, wires, plugs, Autolite plat, MSD Coil, AC Delco wires figuring it was time for a tune up.
-Over the weeks truck began to act funny and idle funny, gave SES light only to find out it was knock sensors so I had those replaced, the next few months I continued to fight this idle problem, cleaned my EGR(seemed to be fine to start with) New AIC valve, fuel filter, cap&rotor
-Between Jan 2011 to now I have redone all my exhaust (including o2 sensor) from the manifolds back, now have cold air intake, replaced my Spider+Nut kit, the last few days it seemed ok untill today when it acted weird like the throttle would be lightly taped then it idled "normal" I reved it to 2000 and it dropped down and almost died a few times and wouldnt idle then I cut it off and it wouldnt cut back on, walked to advanve got a new ignition coil wire put it on and it started, so make sure the old one was bad I put it back on and cranked and it started too!.
-----ISSUE AT HAND-----
Truck runs great when up and go, Tac ALWAYS twitches 50 or so rpm at an idle after is been warmed up, sometimes it bogs down and acts like it wants to shut off then jumps back up to 1500rpm and drops to 250-400 and jumps itself back to 1500 and repeats, almost like the throttle is being fanned and it stalls. When the turn signal is on the voltage gauge and oil pressure gauge and rpm all twitch slightly when the light flashs (all in sinc and happens all the time, is not periodic, other problems are periodic)) and sometimes when its put into gear it bogs down and a few times it wants to stall out on acceleration and coming to a stop. someone PLEASE help me, I am at a loss for words, this is my daily driver my only way around, and to make matters better Ive been laid off for over a year, I have no idea what to do.... I long for the days of feeling like my blazer was unstoppable, now Im scared to drive down the street without feeling like it will die random. Some days are problem free, other its a pain.

One more thing, it seems to idle rather rough some days, Its not perfectly smooth, but enough to where you feel it in the seat and it shakes the antena hard

 

While you had the motor all apart, did you clean the throttle body, specifically the IAC valve & bore? Any vacuum leaks? Any codes present?

Also, we have a nifty feature called 'EDIT'. Please do not double post to add a little stitch of info. Instead, edit your post to include it. Thanks!

 

I didnt do the engine myself, a shop did it for me, but my throttle body does seem rather clean, Ive cleaned it myself and its been cleaned for me by them, the IAC valve is new, havent noticed any vacuum leaks, but out of curiosity how would a do it yourselfer go about that? just spray lines with soap and water? and no codes, the only codes that have been pulled were the 43, knock sensor codes

 

Did you clean the IAC bore when the IAC valve was replaced? It still could be getting hung up.

As far as finding vacuum leaks, carb cleaner or an unlit propane torch can be used to find a leak. You will be listening for a change in the sound the engine makes. With carb cleaner, just spray along gasket surfaces and vacuum lines. With a propane torch, trace along these areas.

 

on the passenger side of the intake manifold i have 2 black hoses ( dont exactly know what they go to ) but both are about an inch in diameter, one seems to jump and twitch ALOT more than the other, i dont have carb cleaner or a torch on hand but could that be an indicater? and the IAC valve was also done at the shop when they had it, so i dont know about the boot, should all that i have to do to check that is take IAC valve off and look or what?

 

Have you gone through and checked grounds? If there is one thing that there cannot be a shortage of is grounds and lack of them can play hell on an automotive electrical system. If you have a meter(less than $10 at Harbor Freight, BLACK wires are usually ground. I would start by disconnecting the battery (make sure connection is clean and tight first because that may be the problem) and checking main components to battery ground cable. Some things off the top of my head are:
Coil->block
Ignition module->distributor base, Dist. base->engine block
Engine block-> ground cable on battery end.

Some sensors ground through the block and some use a ground wire. If nothing turns up at least you've covered the bases and know there is no problem there.


Vacuum leak is a good thing to check as well.

 

i was check as to what causes this rough idle issue andy have i think i may stumbled on something, on the driver side of the intake manifold past the throttle body is a little black "sensor or something" has two plastic small prongs on the back side and an electric connecter on the side, on hose has a 90* elbow and goes to this male prong at the bottum of the throttle body, the other goes back behind the intake manifold so something i have a hard time seeing what it is, well sometimes i put my hand on it and i can feel a click/ticking inside of it, other times there is no click or ticking, what is this part? could it be an issue? after finding the part online that looks like it i think its a "canister purge valve solenoid" am i right? is this a vacuum part?

 

A picture is worth 1000 words. But from your description, it sounds like you may be describing the EVAP purge solenoid which would have vacuum to one side of it from the intake manifold.

 

this is the pic you asked for, its not the best because im not go great at loading images to the net but i think i did it right, anyway im pointing at the black box between the manifold and oil cap, you can see the plastic line on the left goes to the back of the intake, while the one on the right goes under it to the throttle body, like i asked is this click/ticking sometimes being there and sometimes not, normal? of is it a sign of failure in this part possibly being related to my rough idle?

 

well, my blazer cost me big today, broke down twice today on the way to a job interview that i never made it too, SES light came on while driving, truck still ran fine, then it went off after about 5 minutes while it was on for about 10, did this about 3 or 4 times, stoped at a stop light in traffic, stalled down to 200rpm almost cut off the jumped forward to 1500rpm, put it in N and reved the engine, after reving throttle stuck at 2000rpm untill i hit the gas again and droped to 200-500rpm almost stalling after i let off the gas, light turned green put it in OD and almost stalled on take off, 20 minutes later stalled at a stop sign and wouldnt cut on for 3 minutes, sat there like a retard for a bit before i got it to start, started and idled at 1500rpm untill i gassed it again and parked at a gas station and it stalled and cut off, sometimes it would start and miss and spit and sputter and shake, others all it did was crank and not fire, after an hour of that it started and idled "normal" 700-800, tach twitching a constant 50rpm, turned around went home, no SES, 7 stop lights, idled normal, made it home, took it to a shop, all the SES was saying was richmix from the o2 sensor, mechanic test drove it, wouldnt act retarded for him, love my blazer, but think our relationship is over, time to get my Jeep Grand Wagoneer back on the road i think, if i can afford it