I have a 1997 OBS with 185000 miles on it and it is making a weird noise. The engine will whistle at high RPM. I can drive the car half throttle from 0 to redline and not hear the noise but at about 3500 or so if i am at full throttle the engine will hiss or whistle. it sorta sounds like a tea pot heating up. the noise stays the same pitch until it hits about 5800 than it changes to a higher pitch whistle. Does not seem to have anything to do with the speed only RPM. My Mechanic said it was nothing more than air coming in through a hole in the firewall but speed has nothing to do with the noise so i thought i would put up this post and see if anyone knew anything.