There is no ONE correct answer. You need boost pressure+whatever your base fuel pressure is. So fuel pressure needs to rise 1:1 with boost. If you run 7psi of base fuel pressure and 7 psi of boost through a carb you’ll have no fuel flow. So the regulator raises fuel pressure 1:1 with boost. So to maintain 7psi fuel pressure with 7 psi of boost you need 14 psi of fuel pressure. If you run 20psi of boost and 7psi of base fuel pressure you need 27psi of fuel pressure.
