Cant explain to well but my 1.2 is only a few months old with a few k on the clock and my dad waved me down as i was driving off today and said my car sounds odd, i opened the door and revved and it was making a hissy / raspy noise from the exhaust. He asked me if it was revving ok cause if it was skipping or jummping (the rev meter) then it could be serious apparantly. But it seems ok, i took it out for a drive, driving it gently and ragging it and there seemed to be no problems, he reckons it could be dirty petrol. Any ideas?