A little grumble. Pretty much quiet as stock at normal throttle. Open it up and it growls nicely. Not enough to annoy your passengers - or the neighbours - but just enough. The guy who did it knew I wanted something subtle and was going to go for a 2" but put on a 2.25" because the muffler was "almost too free-flowing". Overall very pleased. If you're after more noise, definitely go the 2.25".
I'd imagine the Apollo would satisfy you, though. I get a good bass sound out of the K&N drop-in cylinder filter in the short intake/standard airbox, but the Apollo should offer even more.
I want some pics of the install, by the way. Still trying to convince myself to go for it, so you're the guinea pig
