I'm using HP tuner, as it was in the car when I bought it, its fine for my use, but with out buying the programmer, you are left to using a dyno shop ( good idea) to tune it,
I've used XFI, and now HP tuner, both work good, with more latitude in XFI
my stock ECM controls the 4L80E, which is programmable with HP tuner. (a big plus!)