Drive pressure is a ratio. 1 or a little over 1 to 1, is best. So if you hit 40 psi of boost, 40 to 50 psi of drive pressure is ok. If you hit 80 psi of boost, 80 to 100 psi of drive pressure is ok. But it's when you hit say 40 psi and have 75 psi of drive pressure that things go wrong.