I have a 99 Grand Prix GT and have been having problems with the car lurching and the rpm's jumping around when in drive. It seems to only be happening between 2000 and 3000 rpms, and only in drive. I have replaced the MAF three different times thinking that might be the problem and have replaced the fuel pump also. It does it most when going up a hill or under light acceleration, like when I have the cruise on or when trying to maintain a steady speed going up hills. It will do it with slight acceleration on flat roads, but doesn't seem to do it quite as bad. I am stumped!! Is this a tranny problem or something else. Please help!!!