I'm having the same problem in my 1999 Escalade. When its hot or warm out it surges at idle, but when in park. Difference is my escalade has the 4L60E not the 80 or 85. I replaced EGR, IAC, PVC, wires, cap, rotor, plugs. Cleaned the MAF and the throttle body. It has the upgraded injectors.
I'm...