The car is a 1990 GTA 5.7 TPI. Runs strong, idles fine, no bog from a dead stop, but if I am driving though a parking lot or somewhere that you drive slow and I let off the gas it dies. It always starts right back up. If I have to come to a quick stop while driving (like getting caught by a light or something) it does not stall, or even try. I have installed headers, Crane cam, AFPR, double roller timing set, removed AIR pump. It is still running the EGR but I did not replace it with a new one, it was fine before the mods. I also added a heated O2 sensor to the LT headers. Any ideas, possible vaccum hose issues?

 

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sry to bring this up from the dead.. but.. first things first.. check your vac hoses, ALL of them.

 

Up from the dead? I just posted this, thanks for the reply. I dont think I have the vac hoses all right back by the dist. What if it is sucking air around the intake manifold, I know I have to re-do it because it is blowing oil out the back at the china wall.

 

Vacuum leaks will definitely cause your problem.

 

Has the battery been dead at all recently ? Clean the throttle plates if so. Sounds like it needs to basicly relearn Idle.

 

found the post a way's down the forum.. Didnt even look at the date that you posted it but yea, i had the same prob and it was vacume hoses.. If your sucking any air other then through your air intake then i would seal it up. Vacume leaks=sucky performance/stalling

 

You could take the PCV valve out of the vacume line on the 90 TPI car and it will still idle. It would mostly likley stall on a quick off the throttle other than a slow throttle return with a speed density car.
EGR bleed off or lack of through the vacume solinoid might be an issue. Originally it has a piece of foam on the back nipple that usually doesn't last to long. I've seen these plugged off or improperly routed vacume lines more than once causeing simular issues. Of the 3 nipples on the EGR solinoid one should be open. That is normally the rear one if I remember correctly.
Other than that, I.A.C. issues - including carbon, Dirty throttle plates, Bad grounds, All the way up to excessive resistance in an injector can cause this.
Still running the same plentum and throttle body combination ?
G.M. changed the way the air flows through the throttle bodies from 85-89 has a direct hole into the chamber. 90-92 has a drop down between the body and the plentum. Any changes in that area will cause idle issues also.

good luck