Thanks Lextech, I may give that a try. I did also find a 4.8L MT file that looks good and I tried it last night. I swapped in a 5.3 engine module but after doing that it was in some sort of limp mode or something. Would only rev to about 1500 rpm etc. I did some analysis and as it turns out, the module that I swapped in was a Flex Fuel version (very different injector tables etc.). So I'm thinking it is the Flex Fuel settings that are messing me up. And I can't imagine just flipping the main switch will help much since there are many other differences.

Does anyone have a 2006 5.3 NON-FLEX with operating system 12582811 ? If so, I would really appreciate it if you could post it up.

Maybe going back to the other OP and using the MT module from Lextech's 4.3 file will do the trick as well. Any thoughts on the best way to proceed on this one?

Thanks!
Todd