I bought my UK MY00 three weeks ago. It was had a 45k service including cambelt (main dealer) the day before I picked it up. For the first couple of days, it was extremely quick. But that seemed to tail off, and now feels like there is hardly any boost (in any gear). Also runs like a bag of cr@p when it's cold, with surging and then no power etc.

Is this a case of cleaning the boost solenoid or could this be something else?