so i jjust installed my My Pro dumps the other day and they are even quiter than My Pypes cat back i had on there. Is there a way i could hollow out or gut these mufflers out some to make it a bit louder?
If there's no packing material in those mufflers, they'll sound the same now as they will 6 months to a year from now. I think MAC mufflers are kinda similar in design to Flowmaster and Spintech muffs, aren't they? ... just fully-welded and chambered mufflers that are pretty much hollow, aside from the baffles? If so, there's nothing in there to "break in" to allow for any change in sound. The only time the sound will ever change is a few years down the road when one or more of the baffles rusts and breaks loose within the muffler, as it often happens with old Flowmasters.
I hope you didn't throw out those Pypes muffs. If you don't want 'em, I'll gladly take 'em off your hands.
If those Pro Dumps are too quiet for you, then I'm assuming you're still running the stock H-pipe or some kind of cat'ed aftermarket H- or X-pipe ahead of them. Switch to an off-road H-pipe or X-pipe and those things will be so obnoxiously loud and will drone so much, you'll be wanting to put a set of tailpipes on that beast soon after. Catalytic converters soak of a LOT of volume and tone in an exhaust system ... especially when you've got FOUR frickin' cats in the system. The difference in tone and volume between a stock H-pipe and an off-road H- or X-pipe is like night and day, even with the same cat-back.