I have a PCM and TCM tuned by Vector Motorsports. If interested, let me know. I paid $350 for it and it made a huge difference. I'd say, if you have a 5.3L, this is a must have- and you can keep your original PCM/TCM as a spare. I pulled this out of my 06 GXP, and believe it will be good in any Grand Prix 5.3L.

PCM/TCM no core - $175 shipped!