depend on how long you want it to last! 20 psi is the outside limit on the stockers past that i am told they melt and alos do not make more boost, 18 psi is still high but a lot of people run it at that level expect... with a dp exhasut bcc and ebv or mnc ` 400+ rwhp on a dyno at that level probably 470 hp at the crank with a 15% loss from friction higher than that requires a single conversion. sooner or later at that level you will ruin the number 2 BTW the fron turbo in sequential never sees more than 10 psi by the way.