How much hp will you gain by changing a stock muffler on a 93 spirit to a pilot catback one if any?

Anything that Opens up the exhaust will free up HorsePower. Just as important as the car needing to breath, it needs to exhale as well. So it would give you more HP over stock, as to how much, I dont know, all vehicles will vary in how much HP it will get. but for a Spirit, maybe around 10-20 if not more.