sounds like you have a mild vacuum leak sumwhere, check all vacuum lines, intercooler pipes etc
if that fails, check your air flow meter (borrow sum1 elses and fit it to see if it still runs the same)
if that fails, post here again and ill keep thinking, theres lots of things i can list but some more obvious/easy things to elimate first before the not-so easy stuff has to be checked, like injectors etc