My 02 Impala is having a similar issue when crusing at any speed, it jerks gently. Its like its missing. I thought it was surging by it doesnt feel like it. So I've regap the plugs and they all had a nice light tan color to them. Cleaned the egr the best I could. Cleaned the IC. Air filter okay. I've had coils go on me b4. When they go, they run absolutely horrible, so I know its not that. I have no CEL on. So it hasnt done a hard error yet to whatever is causing it. This wasnt a sudden thing, its started lightlly probably a month ago. Check vacuum lines quickly but didnt see nothing. It almost feels like the crank sensor but dont know for sure. Its not the MAF either. Is it maybe a MAP sensor on its way out? Can you clean them? Any ideas? Ya that was the other thing, I thought it might be my transmission, being a 02 they are not interchangeable with other years with impalas.