I'm having a similar issue with my 1999 GTP. Everything is stock on this car at the moment. The problem started manifesting itself after I had one of the little plastic heater core elbows blow out. My alternator shorted out during this and had to be replaced. I'm wondering if this scrambled something in the PCM. My RPMs bounce about when the tranny hits third and the RPMs drop to between 1500 and 2500. Anything above or below that is not an issue. I know this tranny was rebuilt at 160K and currently my car is at 226K. I was planning on taking it in to have it flushed since I don't have a record of when that was last done. Will they reset the adaptive shift during that process or will I need to ask to have it done.
