Anyone have problems with brakes and high boost?

I am looking for info on the implications of high boost on the braking system of mustangs. I am upgrading the 87-93 brakes to the newer cobra brakes, and my brake guy is curious about the effects of 12-15 psi of boost and how the brakes will react. He is thinking I need to go to a manual brake booster and get away from the vacuum booster that is standard. I am not aware of the vortechs having any effect on braking problems and think it is being worried about for nothing. Any thoughts?

I myself have never seen any effect, your brake booster has a check valve and I have seen automatic cars hold the power brakes at the line with 20psi from a turbo.