1997 Blazer 4.3l CPI v6 4door 2wd Automatic Transmission non-California emission. 193,000 miles

Here's the problem, it intermittently runs rough, gives error codes p0108, p0300, p0301, p0174, p0171(Today). This has been going on for a year(p0300, p0301, p0171), I address the issue it goes away for a while then comes back.
I have also included the fixes I have found for the benefit of others who experience the same problem.

TIP: Whenever clearing codes, afterwards disconnect battery for five minutes then reconnect.

Using a Launch Tech LAU6830 OBD scanner
http://www.etoolcart.com/obdbook-obdii-auto-scanner.aspx

Here's what I have done thus far:
2/2010 bought the vehicle
4/2010 Replaced all spark plugs, wires, cap & rotor, belt, air & fuel filter, oil change(Dealership parts)
9/2010 Vehicle was running rough, multi misfire codes p0300, replaced Fuel regulator and all plenum gaskets cleaned the spider, replaced Battery.
3/2011 After sitting for a few months, Replaced Fuel pump, and fuel filter Ignition module switch, oil change, Fresh fuel, and emission inspection.

Issue: Running rough starving for power, cyl. 1, multi misfire and lean codes.
Resolution: Replaced Plenum Gasket and fuel regulator

Issue: No start, cranks but no fire, No power to fuel pump or relay, No dash lights(start up dummy lights), unable to shift to neutral or move shifter, Battery dies weekly(3-7 days).
Resolution: Replace the Ignition switch module

Issue: Fuel pressure at ignition on and Idle 40psi and below
Resolution: replaced Fuel pump, clean tank, replaced fuel filter

Okay here is what I am dealing with now, three days after replacing the fuel pump. No error codes in three days, purred like a kitten for three days. Then today(After driving on freeway and running errands, stopped and started 5-7 times) it wouldn't do over 15mph, but showed it was doing 40mph on speedometer. Gave error code p0108(First time I have gotten this code) Ran very rough, and had moister coming from exhaust.

Testing sensors and wire harness(MAF, IAC, IAT) found MAP sensor low voltage and carbon build up, replaced MAP sensor. Still running rough retested new MAP sensor, passed.

EGR testing:
Disconnected wire harness EGR, ran rough
Removed EGR cleaned can of air, razor blade carbon build up, pressure test piston.
Connected EGR wire harness but did not install EGR back in engine ran smooth at high RPM
Capped EGR opening with EGR harness connected, ran smooth at idle
Replaced EGR valve

Fuel pump test readings:
Ignition on 59psi pump charging
Ignition on 51psi pump charging complete
Idle 55-60psi
Ignition on, engine off 52psi
Ignition off, key removed remains at 52psi

Catalytic Converter Testing:
Removed Oxygen sensor before catalytic convertor to rule out cat failure by allowing exhaust to "breathe" no change in rough Idle. Reconnected O2 sensor.

Misc:
Checked Battery connections including block ground
Replaced any questionable vacuum lines
Fuel Is Chevron regular
Alternator Test within specs
Replaced Air filter
Passed emission inspection day after replaced fuel pump
O2 sensor Bank 1 appears to have been replaced recently, No rust present.

After replacing the EGR valve it started "Knocking" 3 times a minute while running smooth at idle tracked knocking. As time progressed it began continually knocking and increased with RPMs. Tracked knocking noise down to drivers side exhaust manifold with stethoscope. Shut engine off when I got a another MAP sensor p0108.

Cleared codes, disconnected battery, reinstalled old EGR wire harness disconnected. Knocking noise went away rough idle though. Error code EGR.

Cleared codes disconnected battery, Replaced with new EGR and connected wire harness. Reconnected battery started up and runs perfect again. Smooth idle, knocking noise gone, No power loss up to 70mph(didn't exceed 70mph), No error codes.

Here's my question what the heck happened, and is this a prelude to another issue? Is there something else I am missing that is causing these issues?

 

So the injector spider is original? That could be stuck shut on an injector or 2...

 

I have not replaced the spider, it "appears" to be the first design version or the original. But again she starts with no hesitation(0-1 second ignition) and is purring like a kitten, no error lights this morning either.