I added a F&N air filter and Dyno-Jet FC with my Growler. If you think the MGP Growler sounds nice you should hear it when it's been tuned. My little 300 feels and sounds like a 600 or better. It added HP and torque.
I just installed this a couple weeks ago on my 2006 r6 and it definitely made a difference sound wise. Now a just need mjs headers, a mid pipe, and a power commander. Can't wait...Definitely recommended if youre looking for nice gp exhaust for a good price.
Super easy to install, came with instructions which I followed. It also comes with the mounting hardware etc. so it really was a breeze to put on.
I installed it on my '12 Suzuki Gs500, and it sounds absolutely brilliant. If you've already seen videos of it on the internet, trust me, the videos don't do it justice. The sound is full and rich, and even better than I had thought it would be.
Overall 5/5 would recommend to a friend.