Whatever it takes to break 600WHP lol. From watching sloppymechanics youtube page (if you dont know it Matt does some amazing things with junkyard motors and low budget), it seems that high boost even into the 20psi range isnt so bad as long as your timing is on the retarded side. Once you start bumping timing up then you have to bring boost back down. So being a street car I want a happy medium. The original goal was 16 to 18psi.
