My 14b does pretty well on my stock z6 with average spool time starting around 2300 rpm. I have taken the rpm's up to 7500 a few times, and the 14b does keep up with it. But you also have to realize that a stock z6 really doesn't have much momentum after 7000 rpm anyway. The most i have taken my stock z6 up to is around 12 psi once, and that was getting on the edge of scary. Unless you have awesome engine management and even better tuning skills and dyno time out the ***, i honestly wouldn't go above the 10 psi mark.