I noticed today that if I'm driving (regardless of gear) and I let off the gas and let the RPM's drop, when it gets down to 4200, it makes this high pitched vibrating noise for a second. It seams to come from my shifter.

 

I have the same rattling, vibrating sound and feel. It seems to me a little lower, around 3500 rpm and in lower in the car.
It's only when I am in gear, coasting down, without pressing the throttle at all. If I give it any gas whatsoever, this sound goes away and I hear my exhaust.
I think it's the clutch springs vibrating. Don't count on my word though!

 

I've read many times about a clutch-buzz problem when decellerating. I know there was a tsb on it for the older models. If the "search" is working, you'll get plenty of information.

 

It's the infamous clutch decel buzz. Goes back to the very first S2000 and the very first day of existence. It's just a noise and has no influence on the operation of the car. Changing the clutch can temporarily end the buzz but it eventually comes back to some degree or another.

 

Comes back?

 

Not sure what your question is.
Yes, the buzz can return after a clutch job.

 

Thanks guys, I'm glad it's not just mine.

 

I understand it can be fixed with the TSB (will search for these details soon because I think mine should be done anyway - never was and it's an 01).
However, it will only come back after a while if it's resurfaced/refurbished, or replaced with another OEM clutch, right?
What if you get another clutch disk (disk only, not pressure plate or the rest of the deal), like the ACT performance disk or something? At $170, it might not be a bad way of improving clutch grip and getting rid of the rattle altogether.
And one last question from me as well - does this sound/problem persist on Ap2 as well? Are the clutches (I believe made by Exedy) the same part number for all years? Thanks a lot.

 

I think you have a lot of misinformation.
First of all, the flywheel, pressure plate has very little to do with this noise. The origin of this noise actually begins in the transmission (in the normal backlash that's there). This vibration transmits itself forward along the input shaft and into the clutch disc. At very specific rpms upon deceleration, the springs begin to also vibrate. It is this vibration that you hear as a buzz (or rattle).
An ACT clutch disc is merely an OEM disc that has been "re-worked". It may or may not still rattle. The vibration is ALWAYS in the tranny. How it's "amplified" by the clutch disc depends on the kind of springs in it. After market clutch discs tend to be even noisier.
Yes, some AP2s exhibit this trait, but to a lesser extent.