It's not loud at all. At idle, it's probably NOT as loud as the OEM exhaust. Under normal acceleration it come alive. Just a nice deep and throaty growl that lets its presence known. Put your foot down under WOT and it's a whole new ball-game..... with absolutely no drone at anytime [even when MDS kicks]
It is a direct bolt-on system and comes with everything needed for na at-home installation.
However, I had my exhaust guy weld everything on. I had a slight issue with a Corsa bolt-on catback exhaust on my 05' GTO a few years back after I installed it in my driveway and a clamp came free [installation fault; not product].
Since then, I've had ALL my aftermarket exhausts welded on by my guy at his shop..... just a peice of mind.
I do know of a couple of 4th Gen owners who have installed the same Magnaflow catbk as I have in their driveway in about an hour or so. The Magnaflow Y-pipe will have to be cut and welded on, however.
Here's another photo for you --