LT1 Diagnostic experts..... Need help ASAP
 

OK I have a friend who has a custom 72 Chevy show truck with an 96 LT1 out of a Corvette. Its is a bone stock motor from Street and Performance with thier wiring. I guess some how it is converted over to speed densidy because there is no mass air on it. It is a OBD II computer with Ed Right program to eliminate EGR VATS, SMOG ETC.

The problem is after running fine for a year it is now all of the sudden the idle is at 3000 and won't go down. He has to leave for a big show in Mississippi in a couple of days. They had it in a regular shop all day and can't find what is causing it. All that said is it must be the computer. He is planning on making a emergency trip to Ed's in the morning if they don't figure it out tonight.

My basic (But expanding because of what I learn here) knowledge tells me it has to be one of 3 things
- big vaccum leak
- IAC solnoid staying open
- throttle blade open

They searched for a leak, replaced the IAC, and the throttle is not hanging. What are they over looking?

Thanks in advance for any help.

Some diagnostic software or scanner data would probably help. It is important to know what the pcm is commanding the engine to do.