Are you running stock tranny fluid? Switching to an aftermarket fluid such as redline (www.myoilshop.com) is a know cure for nochy tranny issues on 3000GT/Stealth's and I have a feeling would probably help you out a good deal. Another really good tranny fluid is GM's syncromesh (no joke!). A lot of 3/S owners have had good luck with this fluid as well.

Just some words of advice from a Stealth owner...

Ted