I have a 1990 Camaro with a 3.1. It idles at around 1800 RPM's. I have to get it smogged and in order to get that done, the car need to idle between 300-1200 RPM's. I changed the TPS already. I see a screw that set's the throttle, but there is a plastic seal on the inside. How do you remove the plastic seal in order to adjust the torx screw?

 

I would look at the idle control motor to make sure nothing is holding it open. Could be built up carbon or a bad motor. And don't mess with the set screw it's preset if you move it it will also move the tps reading. You could also have a vacuum leak causing your high idle.

 

The base gaskets for the tbi have been known to go bad, that would be a good place to start so you can really clean up that tbi unit.