2002 Honda S2000

Noises problem
2002 Honda S2000 4 cyl Two Wheel Drive Manual 91,000 miles

My 2002 Honda S2000 has an annoying high-pitched whistle or squeal when accelerating through about 2,500 to 3,500 RPMs. I can't be 100% sure of the timing, but I believe it started after having the serpentine belt replaced at 90,000 miles. I took it back to the mechanic who replaced the belt and he could not pinpoint the noise. I took it to another mechanic who swore it was the catalytic converter, which I had replaced for $1,100. It did not fix the whistle. Any thoughts on how to get rid of this annoying squeal?
September 20, 2009.

Is the AC on when you are driving, turn the AC off when driving see if the noise is there.