I just found out that my throttle body is not for the GTP, it is a throttle body from a 3.1/3.4L, I'm guessing from a Grand Am. Would this affect performance at all? It is quite a bit shorter than the stock GTP throttle body.

Also, could this be part of what is causing my car to run weird? It is now trying to die constantly, dropping to about 500 RPM, unless I keep the throttle open. I don't believe it is a vac leak, I cannot find one anywhere. Just replaced the IAC and no change.