Had the same problem, the three way switch on the Xfer case was hooked up wrong making the engine suck vacuum through the vent hose. If you want some detailed pics I can upload them.

 

Vacuum lines should be (4WD CPI):
back of manifold---short pc of hose---"Y" connector (extra fitting is purge canister vac line)---short pc of hose---check valve with four outlets (1. vac ball, 2. heater ctrls, 3. cruise ctrl, 4. xfer case 3 way valve)

make sure there is a hose coming from the top of the purge canister is connected to the front of the intake.

 

if you could get me pics that would help out alot man and i think thats whats missing, the piece from the intake into a Y. my check valve only has 3? the front line is connected.

ill look further into the rest as soon as it gets back from the shop, i had a terrible noise coming from the front of the engine, the tensioner pulley's bad and apparently when they did just their basic diagnostic it was running way too cool. so waiting to get it back monday.

 

Do you know what is suppose to plug into thr rubber booted plastic line? I got everything connected but that

 

Depends on where it is - could be to the vacuum orb ... or direct to the throttle body .. or into that check valve ...

 

its comes up from behind the engine, its the line in the third pic of the ones i uploaded.

 

Update: i replaced/re-ran some lines and replaced the check valve with a new one of the one thats in the pics. but i have no vents, any suggestions? is there a different kind of check valve? someone said something about a 4-port valve but i could only find one like the one in my pics

 

http://www.amazon.com/gp/aw/d/B000C9C82W/ref=redir_mdp_mobile

here is the 4 way chk valve on Amazon.

 

Throttle body idle set screw is preset. DO NOT ADJUST! You're begging for problems if you do.

 

I dont have a tbi, mine is cpi