Edit: Problem solved. The temperature was about 5 degrees when this happened. It went away when it got warmer, so either something was frozen, or the car just made a ton more power when the air temp was that much colder... Either way, seems to have resolved itself.

I've read before that some R53's go through clutches fast. I also have a good amount of performance work done, so I assume this will take a bigger toll on the clutch as well. I've got 64,000 miles on my 2004 and it's started to slip if I get on the throttle while at a lower rpm in a higher gear. In other words, if I'm cruising in 6th gear at 70mph and I want to accelerate to 80 without downshifting. If I give it more than half throttle, it will slip between 3000 and 4000 RPM's, but not before or after that. The same thing applies in 4th gear at 35mph. It only does it for a second and then catches again. If I downshift its fine, and if I'm over 4000rpm it won't do it. Has anyone experienced this? Is it the beginning of the end for my clutch?

Thanks for the help!