When I think of Tail I think of wastegates since that is what we use on most of our custom built turbo set ups on other cars. When you said 50mm I was thinking that was way to big of a wastegate since we use the 34mm most of the time. But like I said....brain fart...the BOV's are nice and would work....also he could use Zen, TurboXS, Blitz, etc...if he is going to weld them on.