I'm running a brand new M5 clutch in my M5. Maybe 2k miles on it. It was broken in correctly and it does hold the power. If you put some heat into it and try to feed it hard shifts back to back then that's another story. I wouldn't recommend it for 500+whp applications.I am definitely not an expert on this, but I remember reading in some other post, a response to this same question that said "The stock (M5) clutch in good condition is reliable up to about 500 whp". Again, this is just "hearsay".
sorry guys, I just realized that this whole thread discussion might be a moot point. I was supposed to get a sprung hub clutch because I am using a single mass FF in this application.
I assume there is no sprung hub version of the Luk or Sachs?
Are any of you running lightweightflywheels? what clutch did you go with?