>"I bought my '08 WR250R used at 5,000 miles with the EXUP valve removed...check engine light..." Sound like you didn't do the resistor jump in the EXUP controller end ($1 from Radio Shack) or buy the pre-made jumper end ($45 12 O'clock Labs). I believe there should be some info on WRRDualsport.com. Post back if you don't find it. BTW: I did the resistor jump, worked fine, no error code. Then I did the pre-made jumper which has a bit more electronics in it. I "felt" that the jumper made a bit of difference... but heck... dunno. Would be nice to perform that test on a dyno.