My brothers 2004 Cavalier is having a problem holding idle. If you start the car it dies right away. If you start it keeping on the gas to keep the RPM's above idle it will hold and you can drive. As soon as you bring it back to idle it dies.

Now if you start the car with the AC on it will hold idle from the extra stress and higher idle.

the car had a turbo and AFC added. The turbo has been brought down to 0psi and the afc was removed over the weekend since the car has been having problems for months now. We figured the issue could have been with the afc. All the problems were related to idle speeds. Some times it would die like I explained above, (some times it would die as you were driving down the road)others it would just hold idle at 3k rpm. Also it would start very rough you needed to make sure the car was completely warm before attempting to drive it or the ride would be extremely rough.

Is there a module that has been known to fail in these cars? Any ideas what could be wrong?

Thank you in advance.