I'm looking at adding a turbo to my 2001 Chevy 1500HD and the common upgrade for the 4L80E transmission above 500HP is to add an HD2 shift kit. Is there anything in that kit that I can't do tuning in HPT? The only thing I see is the pressure relief valve, which is weird in the HD2 kit and I was planning on using the Sonnax boost valve, which does the same thing, instead. Pressures and shift times are easy enough to change in HPT, so what am I missing? Thanks.