Ok, I'm about to buy a 1989 RX-7 Coupe N/A. It is in very nice condition with 63k miles. It needs a new clutch which is being replaced before I buy. One problem, the guy says it is 'sluggish' after 4-5k RPM, sometimes it will shut off, sometimes just no more get up and go. It's not that fast under normal RMP either. (this is not because of the clutch, it was like this before)

Vaccum? O2sensor? Intake? Plugs?
I'm not that familiar with rotaries, so Im just making guesses from a cylinder engine.

Only mods I know of is exaust, no cat converters...

 

The 5th and 6th ports might be stuck shut and when you get above 4000 rpm they just aren't opening up to let more air into the engine.

 

sounds right.. 6 ports.. i wouldnt know if that would shut it off or not.. hmm

 

Ya , I just reread the post.. It would be a cause for no power above 5000 rpm, but the stalling out could be due to lack of compression or a full blown seal...