I used Vader's procedure to set the minimum idle air on my 88 Camaro 305 TPI.

Before when I set minimum air, if you adjusted the screw too far then the car would stall. My mechanic recently cleaned my throttle plates with a cleaner. Now, even with the screw turned so far that it's not touching anything, the car won't idle lower than 600. I've replaced the IAC, to no effect. I should be able to get it to idle at 450 (like I used to).

I prior owned a 89 Camaro, TBI, and had to have the throttle body rebuilt, as air was entering through the bushing on the side of the throttle body (by the throttle linkage assembly). I was getting a code, and the car ran like crap.

This one runs fine, and my mechanic was unable to find any vacuum leaks when he was prior working on my car. But there is a little play in the bushing on the throttle body - is it possible for the bushing to leak enough to cause a problem but not throw a code on the MAF?