I'm planning on buying a Greddy BOV type S.

But I wanted to know if I needed a buy a Outlet adapter?

If so what size do I need to purchase 16mm, 19mm, or 29mm.

Right now my evo is completely stock.

I've also noticed that the different Greddy BOV has recommendations ... amount of horsepower should I follow that or just continue with type S?

Thanks,