I have a Mac ss catback and jlt rai on my car. The catback I did not notice or expect a hp gain. The RAI I actually did notice some more pull on the top end. How much of a gain can I expect from a MRT catted h-pipe? The stock midpipe with those cats seems to be one of the more restrictive bolt ons on the vehicle. I would think a new h-pipe would offer a decent HP gain. Am I right?