I have a red rx7 r1 and I have been very happy with it up until a few days ago. When I accelerate there is a strage hissing noise only at high revs. I am aware of the blow off valve but that only occurs when you let your foot off the gas. I will try to fix the problem if anyone can give me any ideas of what it is.Thanks!

 

sounds like a BOOST leak check the rubber couplers on the Y pipe and IC to intake Pipes for splits or loose clamps , also check for loose hoses in the RATS NEST under the intake Manifold.