I tried a B&M kit in my 200R4, and didn't care for it at all. Poor shift quality and inconsistent at the track.
I called Chris, at CK Performance and he set me up with a "SHIFT RECALIBRATION KIT W/ GN SERVO #24RSRK/B".
http://www.ckperformance.com/resources/GM2004RSHIFTKITSVALVEBODIESGOVERNORS.html
I don't want to sound as though I'm advetising for CK Performance, but I was so impressed by the way my trans performed after the install, that I will throw as much business as I can his way.
If you call him, expect Joe Pesci to answer the phone...Chris has a very heavy New York accent. Dan