Yeah being a good co-driver is a delicate balance, particularly if you are driving someone else's Mustang. I blew a guys motor once, and never felt worse. I try to always give my co-driver as many tips as possible, ideally he would finish a tenth behind me, not 5 seconds a lap. Obliterating someone in their own car has to get old after awhile. We all have egos, but to me racing at this level should never be so competitive that winning a three inch trophy means more than helping a buddy.