its easy. I have a modified wrx catback with a prodrive muffler. I removed Prodrive axle back. Cut the muffler off a wrx axleback, welded (clamps will work) on a piece of straight pipe and a chrome tip. Bolt that back on at regular axle back location.
when its cold it farts barks and spits waaaay more. And while cruizing at very light throttle it is actually quiet. Push in the clutch while cruising and smack the gas and it sounds like something broke. So, when Harley Davidsons go by I push in the clutch and goose it. It makes that popping rattling snapping sound and they all left off the gas, hit the brakes, and look down like something broke on their Harleys.