Turbo Idle Problem

So the car is a 92 with a complete custom harness by guru joe, using a wet turbo from an xr4ti and an engine from an 86 SVO, and a LA3 computer and stingers front mount and the large vam and injectors with a cone filter on the end of the vam. That is the motor, anyways, when I start the car seems to idle fine, I put it into reverse, let out the clutch start to back up and have to keep goosing the throttle to keep it from idle searching and dying. That is only the begining. sometimes when I come to a stoplight the idle will chill around 1500, and the next light I come too it will idle around 800 a little rougher, the next light might be 1000, and then possibly the next light might idle search and die again. Car sometimes bucks while cruising on the freeway at a constant speed, Car feels very fast under WOT and once in a while will hiccup ( miss/backfire slightly) while I am accellerating hard. I can live with the hiccup but the random idling is driving me crazy. If the car begins to idle search I can rev it to like 4000 then the idle will stop searching and usually hover around 1100 fairly smoothly. I cleaned the IAC, the idle acts pretty much the same, searching even with the IAC unplugged! I also set the TPS voltage many times too. I tryed reseting the computer. Where should I look next, hopefully not a cracked head or blown headgasket, car is not overheating. Thanks for your suggestions.
 
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i had a something like this happen vacumn leak at the hose to pvc valve,cracked hose a the intake fitting. Also the vam I got off the 86 turbo had the spring set too weak I thought it was bad tried another one solved problem. So I compared the two and found the flapper in the vam moved to easy popped the cover off it, changed it. Now ok. This was on a small vam hope this helps
 
On mine it's a square plastic cover. under it is a gear with u shape wire that is mounted on one and the two tips of the wire is in the teeth of gear. I just raised the two tips up and move gear for more tension. I recommend you mark it or count the teeth so you put it back if it doesn't help. No use making a second problem if this does not solve it.Make sure to seal cover back you don't want water in it. I don't remember how much I turned it near as I can remember it was not much. Hope this helps
 
I just thought of something check rotor button. I cracked one where it goes onto the shaft once letting it be off time drove me nuts. But it was my fault I broke it putting the ignition cap. Good luck
 
I took off the cover of a big vam. Looking at it wiring toward you plastic cover off . Only 1 wire of u holds the wheel. With vam door shut right hand of u is in the notch of the 3 of 023. Also found a website how to set the sweep. Turbobird.com under FAQ. Listed as vaf mod for 88 tc. Good Luck.
 
What ended up fixing this? My car is doing the exact same thing. I've even put brand new injectors and a new FPR in yesterday. I can't handle the guessing game anymore and my car is doing this EXACT thing. It's usually fine when it's cold and the longer you drive the worse it gets.