Noooooo not my tach

Ok i got a problem with my stock tach. the other day i hit about 135 in my friends 90 tsi awd, racing a 300 z, it went well other than the rev limiter in 5th gear just bogged the car and scared the shit out of me. Anyway now the tach doesnt seem to be working right sometimes its fine, other times its not, mostly not. It will read normally as i accelerate and then act like its hiting the revlimiter at like 5000 but the car still revs and continues to accelerate. Please help if you can.

Check the sending unit for it. If that is giving the right signal then it is the tach.

Where is the tach sending unit located??? please