Here are the particulars. 1990 Coupe, stock L98 with about 95K miles.

About two weeks ago, the Vette started idling very rough, particularly when warmed up. It seemed to "surge" at ilde and up to about 35 MPH, then it seemed to smooth out some. I took it to a local mechanic and he found that the vacuum line to the EGR was (at some point) incorrectly installed and the EGR valve was not functioning ... at all. He also found that the IAC valve was not operating correctly and that the #8 plug had a crack in the ceramic. All items were then replaced with genuine AC Delco replacement parts, the throttle body got a good cleaning, the fuel filter was replaced, and everything was put back together.

When I picked up the car the other day, the mechanic told me that the idle was still a bit rough, but that should smooth out once the computer recalibrates to the new parts and improved vacuum. He told me that everything else checked out fine ... injectors, fuel pressure, and all of the other diagnostics. I drove it this morning up the interstate for a while and then rode back into town. Honestly, I don't think it's running (idling) any better than when I dropped it off at the mechanic and it still seems to surge, particularly when it's warmed up.

Is there any truth to the claim that the computer will recalibrate to the new parts/improved vacuum? If so, how long will that take? Do I need to run a tank or two of gas before I notice a difference?

 

i bet you have some bad injectors, the multecs that are in your car have 95,000 miles.. get your self an ohm meter and check each injector hot. I bet the shop only checked them cold.. if they have less than 12ohms of resistance they need to be replaced. Multec failure is so common to these cars right now because they cannot take the alcohol in the fuel.
do the test and report the results.

 

One @ 13, Two @ 14, Three in the low 40's, One @ 50, and One @ just under 100. New injectors by weeks end.