right so hears the problem was out last night and decided to put my foot down and give the old girl some speed and it kept sort of shuddering now and then but then when down our local bypass and put my foot down and it felt as if some one had gone in the back of me but after i slowed down after panicing a little i went on boost again and was fine i checked the bov incase was leaking boost and its all on there nice and tight.am i right in guessing its a spark problem maybe the plugs are shot?revs up on the spot fine no misfiring are anything.bit confusing really