You do't have to rev them much past 7500rpm. After that it's probably more noise than performance. The idea is to shift so the revs in the next gear is at your torque peak (probably about 4500rpm). I don't know what the rev limiter is on my 4age., but I know someone that hit 9000rpm in an early model mr2 4age and he never hit a rev limiter so be careful. You don't want to blow your motor on something silly