Alot of help please 89 probe gt
 

I have a 89 probe gt turbo. and it has been a nightmare, i love the car but the problem is. 1st: when i bought it , the kid before me had added all this crap to it, venom computer thing, (i keep it off). a blue psi (to increase or decrease the turbo). cold air, . and i was told bigger injectors. well when i bought it the exhaust was off and the turbo would cut out then kick in. so i put one on it. and it fixed it a little. now when ever the turbo kicks in it backfires and cuts out. and it jerks u back and forth untill u lay off the gas. some times its not that bad. but 90% it is. i love this car and just want it to run right. i have done plugs and wires, cap and rotor. also fuel filter. we checked the fuel pump and it was in the right range. it seems to be running to rich. i work at a shop and even our head mechanic is stumped, he thinks its a vacuum leak some where and we have looked all over. the check engine light comes on only when the jerking starts then goes off. please so help !!!!!!