NEED HELP FROM COMPUTOR GURU!!!

OK, here is the deal with my 1992 B4C 5L 5 speed. My engine is running at high idle, sometimes bounces from 2000-2500 rpm. I have checked/ replaced map sensor, IAC, TPS, EGR and evap canister--still have problem. When I check the engine wih my Tech 2 tool, I have 0 position on the IAC, but when I hit the throttle, the IAC moves. It sounds like a vacuum leak problem, but I cannot find the leak(I have been searching for it for a long time). The only places left to check are the intake manifold to head gasket and injector O-rings. Someone said once that an injector could be out of balance, but I cannot check for that. I know that the engine has been replaced because it is painted orange and some of the electrical connecters were broken

PLEASE HELP, PLEASE!!!!!

 

does sound like a vacuum leak,simply spray a flammable penetrating oil all around the gasket areas and the injector seals. to get o iac counts usually the leak will be close to the iac valve.also check the throttle plate and clean any black build up that my be in there.keep a fire ext.handy for safety reasons.good luck