I would second the upgrade to the 411 PCM. The wiring swap is not tough and the tuning capacity is considerable. I did my first upgrade to the black...
Been playing with the latest v8 and scan/tune v3 for a few weeks now. I started with my stock 1999 Yukon 5.7l vortex that needed the engine rebuilt....
There isn't a lot of information on CAX files, and even less on CAX8 files. Probably for good reason; it's a way to weed out the ones that shouldn't...