hi, iv got a mk2 gti 8v digi and having issues getting over 70mph. Car runs fine through 1st, 2nd and 3rd gear, but in 4th and 5th the car (i guess) is misfiring/juddering and have no power at all. I litterally cant accelerate in these gears without it happening. iv changed the leads, cap, plugs, air filter and oil filter but still the same. whilst it does this misfiring my headlights will flicker (when on) and just to add to this iv twice had a mass of white smoke pouring out when i have managed to get it goin over 5000rpm at which point i lose all power till i let off the throttle and all is fine again. Somebody help!!!!