Ok, thinking about creating a VG36-37 (to get around CARB rules) to eek some more power out of my VG as I slowly make it an off/on road toy.

I can't legally use headers for my vehicle on the street, so I was thinking of porting the stock exhaust manifolds to help them flow as freely as possible. If do bore and stroke a VG, I want to waste as little of the increased HP from all the effort required.

I understand the potential problems related to fluid dynamics, but I was more curious if anyone has done this and what issues I might possibly run into by grinding some of the manifold wall away.

Thoughts anyone?

we do this all the time on our subaru manifolds. You probably won't gain as much as we do, but having a nice smooth wall on the manifold will be a nice addition and free up some ponies. And while you're at it, you can do what i did and smooth/polish the outside too. Looks really really nice. Port match it to the gasket and then smooth the inside wall with some nice smooth radius work and you'll be set.