I don't see where the input pressure would make any difference as long as it can keep the regulator supplied adequately. The regulator does just that, reduces pressure to the set 5 or 7 psi. So at that point it is a constant value, based on the size of the smallest restriction, the needles and seats. 5 psi or 7 psi (more pressure, more flow, which there is a formula for) will flow xx amount out of that small restriction, provided the regulator is doing a perfect job. This is assuming the feed line and regulator to carb lines are more than adequate.