whistling turbo

I have a 2001 sport and a friend of mine has a 2000 SLT, They are both 4x4's quad cabs. I have been doing some work on her 2000 and notice a big difference in the way they run. We have different upgrades, but i don't know if this makes that much of a difference. Mine seems to have all kinds of power at low rpm's..say 1400-1800, and hers seems to like 2000-2500 rpm. I know I have the hy35 turbo and she has the hx35. And she has tst powermax 2, and I have hypertech. But I am wondering if my tranny has an upgraded valve body? The only thing about my tranny that I don't like is when in 2nd gear it just don't seem to put the power to the rear wheels. Other than second gear it pulls great. It stays in overdrive even when doing 50 mph on pretty steep hills with an rpm of 1300-1400 and if I ease into it, it will pick up speed nicely. Don't seem to slip except 2nd gear. Hers on the other hand shifts down alot easier, It shifts down out of overdrive when I don't expect it to because mine don't. Seems like mine has unbelievable bottom end and hers has nice mid-top end. How can I tell if my tranny is upgraded? And do you folks think the different mods we have would make the differences between the two. Or does one of us have issues?