Yeah, it all depends on the dealer but before they make any decisions on major issues a Subaru rep usually comes in to look at the car. The one I delt with was more understanding because he was a drag racer, and he understood the mechanics of the car, and how it worked. All I have is a cat-back and intake, and the dealer tried to void my warrenty. But the rep knew that that wouldn't cause the transmission problems I was having, and he got my car fixed. So if they try to void your warrenty, ask to speak to a rep, but I wouldn't mention that you race the car.
And I've never heard of valve float on a WRX. It happens alot on Eclipses and Civics. That's interesting.