So did some head work for someone who said his car wouldn't hold any pressure during a leak down test on cyl #4, leaking it all out of the exhaust side.

For anyone who thinks its not harmful to install and run even a mild upgrade like a 16g and turn up the boost, here are two pictures. The first is what a valve should look like. Bad macro shot, but a smooth surface.



This valve is out of his head, after attempting to tune his 950's and about 20PSI on his 16g.