if your piping is 4 inches, then there is only one way to fix it...have a 2 inch exhaust made. or order a cat-back, but thats way more expensive. if your piping is 4 inches, that high pitch rev noise is your intake gasping. it can't keep up with the volume that the exhaust can handle, creating almost no backpressure. this throws off engine harmonics, the ga16de has to have SOME backpressure to function properly. hope this helps, let us know about your pipe diameter.
Yeah I was going to mention that about the lack of back pressure. I t really hurts low end torque. That is why unless you have a full out race car it doesn't make sense to gut your cat. High flo exhausts for large displacement V8's don't use any thing more than 3inch.
no no no...its like a 1.25 piping with a 4 inch tip and like 2inch inlet and when i punch the gas and go up to 3100 rpms it goes to a high pitch rev noise than 3000rpms and below it makes the deep exhaust tone