I just noticed this about my 96 GT, if I get on it to pass someone, or drive a little rough, when I return to normal driving it starts missing pretty bad and then the engine speed will surge at idle. Drops to about 400RPM and then back up to 1K RPM. If I drive it normal for long enough, it smooths back out on it's own.

I am also getting an EVAP malfunction code. I have found a few broken vacuum lines, but I am thinking that I am still getting leaks. What is your opinion of what is going on?

 

It sounds like a vacuum problem for sure. Did you fix the broken lines?

 

Fixed the lines and almost fixed the problem. It will barely surge now. Must still have a leak somewhere, but I can't find it.