I fitted a GSR kit a few months back, took me an hour if that, slight pain as you have to remove front wheel to remove stock unit, but very straight forward, and very obvious perfomance gain, just feels more responsive, and turbo seems to spin up faster plus, you can hear the stock dump valve, and get all sorts of lovely whooshing noises. I also fitted a TMC Motorsport tuning box, which in combination has been excellent. Going to get CAT back exhaust sorted in next 2 or 3 weeks, which should have me up around the 190bhp mark.