I'm having the same issue with my GTP. It has 162,000 miles on it. The RPMs don't jump when I'm accelerating but it jerks like it can't decide whether or not to downshift. If I step into it, it down shifts and does fine. It has felt like it slipped twice when starting from a stop too. No SES light. Once in a while I get a ABS light or TC Off but I'm pretty sure that's a separate issue. Have you had any luck getting it fixed?? I've heard it could be a PCM problem, TCC solenoid, plugs, wires, coils, or the transmission going bad.