An interesting occurrence over the weekend at the track. Oil started collecting on top of the timing cover. Normal running in the pits, no obvious oil leak. The oil only appears after a hard run. It started appearing with the latest increase in boost level. It seems to be trailing from the front end seal of the lifter valley cover. After some thinking, I figured out that crankcase pressure is building enough to push up on the valley plate and affect the end seal. Next PMing of the engine, I'll be increasing the thickness of the valley cover plate and looking into using a different model of rings. Those that are building their own intake, pay attention to that possibility.