My N/A's top end (6000-8000 rpm) is quite rough, and it really loses power. There is also quite a bit of vibration up there (above 6k rpm). The car drives very nicely (though perhaps a little down on power?) up to about 6k rpm. It's got 166,000 miles on it.

What could be causing this?

Ignition?
6 ports? (would that cause the vibration?)
clogged cat (vibration?)

???!!

Thanks!,
Manolis

 

When was the last time you took out your fuel injectors and have them cleaned professionally? With a car that much of mileage it is usually a good idea to get them out and get them cleaned. Also, replace the o-rings while you are at it.
Check out this thread.

http://www.rx7forum.com/showthread.p...light=3800+rpm

It has a step-by-step of removing your fuel injectors and other things you can do yo tour high mileaged car.