hello for last couple times i decided to take bowser out in the wet he has developed a misfire. start up fine leave to warm up and runs abit rough, pull away and its sluggish then all of a sudden the power comes through. its constant until it warms up or been driving for bout half hour. had the same prob with my mk2 and that was the dizzy, replaced that and it was fine. could this be the same on bowser? he has had new leads and plugs fitted