Thanks I think that seems like the best way to go, I may use the mill though it just seems like it would be easier to set up. I was thinking of grinding an old endmill for the job, do you guys think a collet will hold it tight enough, the one I have in mind has a 16mm shank, would it be safe to put a piece of aluminium behind it in the collet to stop it sliding back

Crusty should I use a twin turbo setup or should I put both exhaust through one turbo