1 psi of boost equals how much horsepower?
If your example engine makes 150 horsepower naturally aspirated, then you can estimate an extra 10.5 horsepower per pound of boost with a turbo and 7.5 to 9 more horses for a supercharger. If you're running 8 psi of boost, then that's an approximate 234 horsepower with a turbo and 210 to 222 with a supercharger.