i made this PGR2 editor about 3 years ago.
It sits on the PC, has full FTP functionality, so you can go from PC to XBOX via ethernet, and does all the slider-type stuff that people ask for with 2 key extras:
1: A full torque/horsepower graph that can be edited in realtime
2: A peak horsepower/peak torque gear ratio converter, so when you hit peak revs, the next gear will drop you straight into peak torque, so you're always on power.
Oh yeah, lots of sliders!