ok, my 89 Firebird 2.8L MPFI V6 is making whistling nioses when i depress the gas more than half way. It is very wierd because it seems like it is comming from the Exaust. I know this because i cannot hear it as well when im at the front of the car as when im at the rear.
Could be your fuel pump working overtime. I had a strage whistle in a Chevy truck I used to own. You could hear it all the time but it got louder as you accelerated. Sounded like it was coming from nearby one of the rear wheels.
Another guess is a pinhole in the muffler welds that is just the right size for a whistling effect.
I second the exhaust restriction. try to install a vac guage somewhere on the engine and SLOWLY raise the RPM. If you see the vac drop as the whistle begins then I would start By climbing under the car with the engine off and car cooled and wiggling the exhaust system to listen for loose internals in muffler, cat and pipes.
heh, i guess it is the exaust then...its really old and rusted in some spots, and there is a crack in the tubing right before it goes into the muffler, should i just take it off for now? this whistling **** is getting annoying.