Originally Posted by zcorvette
After changing gaskets, you need to balance your TBs at 6" WC and set the base idle at 525 rpm using the throttle-stop screw on the driver's side TB. The computer works from there to fine tune the idle with the IACs. If you need instructions on this, search the Corvette Fever website and/or Crossfire Injection Forum.
If you've already done all this, I'd look for a hidden vacuum leak.
You may or may not need to balance the TBI's. The air /gas mixture is very sensitive. First see if the the caps on the TBI's to access the adjustment screws are out. Previous owners sometime mess with the balancing to adjust for a gasket leak. If this was done before then yes you do need to balance them.
The TBi's come balanced from the factory adjusting them is a bandaid solution for other vaccum leaks. So if you caps are there don't adjust. the cause is something else.
I assume you unplugged the IAC's to get at the gasket. You realize the IAC's will not reset until you go for a drive at about 35 mph for about 5 miles. Your idle will be higher until you do so.
Did you plug all the hoses back in? Including the one that goes to the air cleaner?
Look for other causes. Is the EGR solenoid okay? No leak?
Not the idle adjustment screw on the front TBI. It comes welded to the shaft from the factory. Is the weld grinded off? If so someone has probably played with it. So if the caps are on and that weld is broken its probably been tampered with. Back it off a 1/4 turn at a time until you get the idle down to about 600.
If the caps are there and the weld is there. No other apparent problem. I would grind the weld off and start with backing off on the idle screw. Remember your starting point incase that isn't the cause.
Did you move the TPS? It needs to be set at .525 volts.
Lastly, how are the throttle shafts? Do you have play in them? Could be a cause of a vaccum leak.