[99LeCouch]

Try your luck over on pontiacbonnevilleclub.com. They're a great group of folks. More into power than fuel economy, but they've broken everything on your and my car (both on the H-body chassis) at least 10x and put it back together. Search around there for a bit, then register and ask if you still can't find the answer.

3800 Series II and 4T60E on your car. My bet is you need some Auto-RX, a fluid and filter change, and an adjustable shift modulator or replacing some cracked vacuum lines.