2003 H2 Hummer, magnuson supercharger, long tubes, mild cam, and meth. This truck has been running on these mods for several years now, runs really strong, 14.1 1/4 mile, with no issues other than the 4L60 it was equipped with would barely last a season. It was decided to do a 4L80 swap this time around. I purchased a conversion harness from PATC . The truck originally had a 12593058 OS, I couldn't find that OS with a 4L80 and ended up swapping everything to a 12613248, it was difficult to find a 1MB file. The truck now runs well and there are no codes but feels unbelievably sluggish. It feels like something is holding it back, you need to use alot of the pedal just to get it moving, you'd swear you were pulling a trailer. Hoping someone can take a look at the tune and shed some light on this for me.