Mike,
Do S2000s have slave cylinders? If so, lube where it hits the fork for the clutch. My hatch had this problem and I thought it was something clutch related. I lubed up the slave cylinder, wah laa.

 

My twin disc clutch sounds just like what you are talking about but its normal

 

Jarrod, yes they have slaves and I thought it was that after I put the clutch in so I lubed it with wheel bearing grease and yeah...same problem lol. I've done some research its all hear-say but ACT's seem to be junk or atleast "not to my standards" lol

 

ACT is one of the highest quality units.
The Aluminum Flywheel causes it to be "more" aggressive than normal, and enhances the Chatter problem more due to the expansion rate.

If you have a Ferrous (Iron) or even carbon metallic pad material on the clutch, you can get that squeaking sound. It's way more pronounced on a ferrous though. I had an ACT 6-Puck capable of 610 lb-ft, and it would occasionally do the squeaking on launch. More noticeable on that when it was cold, or when trying to "ride" it a little bit.

The chatter didn't occur cold, but when it heated, and if you drove it around town for a period, it could get bad. ESPECIALLY if you were running the A/C in conjunction on my car. I had a steel flywheel, and it was bad. My fiancee has an aluminum, and it's worse! It's a completely different make too! I felt fortunate I didn't have the problem some with the 4-pucks had, which is it trying to grab to the point of rolling through the brakes at a stoplight, and having problems stopping with the clutch fully dis-engaged....