Andy, I think you're right. I guess with the WRX, it's more of a factor because it's a turbo - which means a LOT of heat when the boost kicks in (starting at 3500rpm but more "on" at 4000rpm).

I too have heard that the whole breakin period (except for the turbo factor) being a non-factor with modern engines. It's so hard to know who's right. Dealers have a tendincy to tell you something because it's the same thing they've been saying since they were selling cars in the 80's.

So I guess I'm back pedaling a bit (now thinking that keeping below 4000rpm is important and that the varying of rpm isn't as critical). But the truth is probably it's not the end of the world if you get above 4,000rpm once in a while during breakin and you won't kill the engine if you break-in on the freeway as long as you take a few side streets from time to time.