When I am traveling at between 30 and 40 mph and I am steady on the gas to hold speed, the rpm's fluxuate a little and the transmittion feels like it is right on the edge of shifting. Basically the vehical gets a surge of power and lets off, surge and let off, once I either get on or off the throttle it stops. If I stay in that mode for a bit it gets more severe and it kicks a little harder. It does this every time and is very easy to reproduce. If I put the tranny in autostick mode it seems to go away for the most part. It also stalled on me while in traffic trying to get up a parking ramp. No codes tripped. I thougth maybe throttle position sensor had a bad spot but I figured that would trip a code. Any ideas? Anything I can try to narrow it down? Fluids are all good and I maintain it very well but my wife drives it so who really knows. Fouled plug? plugged injector? any advise will help.