Picked my car up yesterday after having this fitted. Sounds really nice, slightly deeper tone at idle and fairly reserved before 4k RPM, after this the tone gets rather sexy and stays like that all the way to the red line.
The flap and actuator in the rear box is not there any more so that annoying "Clunk" has gone and you don’t get the tone change when it opens under light acceleration. All in all I am really please, it is not a neighbour waker around town and back streets, it just rumbles away just nicely with a sporty rasp that is pleasant and not offensive, but get it on the slip road and floor it and you think a Ferrari has just pulled up the slip road along side you. Hit a few tunnels and WOW, what a nice sound.
I dropped my ITG air filter back in when I got home last night, but haven't really had the chance to rag it properly yet round the usual roads I "play" on. I would say it seems to pull slightly better lower down and what little lag there was seems reduced still further.
So I am very pleased with it, the sound is "Quality" and not over the top, in your face "Boy Racer" but it is noticeable louder and when you want to hear as well as feel the power.