Idle Surge
 

I was scanning a local guys car last night and my laptop died so I didn't get to see what was going on.

His car is all stock except for a Lingenfelter CAI and Magnaflow Cat-Back. 93 Trans Am, A4.

Once the car is warm, a sporadic surge at idle will happen. The RPM's will jump up to 1500ish and the car will surge forward on it's own, then it will settle down. A few seconds later (15-25) it will surge to maybe 900-1000 RPM a couple of times, then give you another big surge to 1500 RPM. When this happens, the lights dim, the tach gets jumpy, and the car kind of shudders.

New things on the car are plugs, wires, opti, pcv.

Any ideas??