I haven't had mine out at Willow or Buttonwillow yet, but it'll get there.
I have done HARD 30-45 min canyon runs though.
I'd say it'd be pretty damn close to Streets of Willow abuse too.
Damn wheels were BLACK when I got home. Soft brake pads.
Racing the car doesn't void the warranty.
Crashing the car while at the track will probably void your Insurance policy.
Even my B6 S4 ran WAYYYYY HOT when out at Willow in the summer.
I have no worries and my 335i will certainly get some track time.
Maybe we can hook up for a day at Leguna ? Worth the drive for me......