interesting problem

The other day I had to slam on the brakes and the pedal was rock hard and didn't want to stop the car (like the booster went bad) then litterally a second later they were perfectly fine
then I realized that this happens anytime the turbos are running at 8+psi? Car still runs great except the bov leaks alittle bit I have a new I just have to get the right flange for it

SOunds like a check valve issue.