havent had any issues wit the itg, besides the ridiculously awesome noise it makes, everyone i have in the car asks what it is and loves it when you give it stacks. mpg wise, i think mine has actually gone up, i have to say i mostly stay off boost and drive pretty gently, both for econemy and for the sake of the car, but my driving style wont have changed much before and after fitting, and i think the mpg is certainly a little better, even taking into account the improvement in mpg from the warmer weather. it definately did take a short while to adapt though, and yes the noise became more noticable after a while too, its probably my favvourite mod, because you can never fail to notice the noise, i barely notice the exhaust anymore