Hello all, I have come across an issue with my truck (1998 K2500 Vortec 5700 4L80E). When stopped in Drive with the AC or defrost (since both run the compressor) the engine will surge. Sometimes it is not by much, other times it will go up to around 850 and try to move a bit. Last week it dropped down to 400, so I decided it was time to try and fix it. I'm not sure what other information would be useful, CEL is not on and I replaced the compressor last May.