I have an 86 mazda rx-7 N'A and at around 3000 RPM's i hear this soft whistle coming from the engine...when i hit the clutch to shif to the next geat it will go away and then when 3000 rpm's comes again i hear it...is this a sign that my engine is going out or that maybe i need to check my air intake system? Please help

 

Might be a vacuum leak.. Check your intake.

 

Could be many things. Have a friend rev it to 3K, stick your head under the hood and find out. Dont' get your fingers smacked by the fan or any clothing caught in there.

My guesses:

-If the frequency changes with RPM and goes away when clutch is engaged, probably the pilot bearing in the E-shaft. Kinda sounds like a supercharger bearing whine...

-Clogged air filter? Wistle from AFM.

-exhaust leak?

http://mazdatrix.com/g2.htm