Stock MAP sensor cutoff is ~11.2 psi.

You are getting too caught up on psi. Don't waste your money on a snazzy boost controller you won't even use. Get a decent wastegate with the proper spring in it and you will be fine.

Like GSSR said, psi doesn't mean anything. You can make 300+ whp on stock internals with a decent tune whether it takes 18 psi on a dinky turbo or 6 psi on a huge turbo.