Throwout Bearing. Most aftermarket clutches use poor quality TOB's. It's best to use an OEM TOB if possible.
If your car feels off, I'd definitely start with a simple tuneup, primarily the ignition system. The clutch could be slipping too. Does it start slipping badly if you get it really hot (several hard launches, a lot of shifting, racing, etc.)? I had very good luck with the JWT 1-side metal disc. You can reuse your pressure plate and replace the TOB and clutch disc.
- Greg -