maybe coilpack as i knw that give up the ghost on mine when i had it similar problem as u soon as i booted it the car would missfire and splutter i fitted a new coilpack and spark plugs and all seemed ok if i was you though i would take it to a tuner thorney or regal as they will properly diagnose the problem saves u keep spending money buying bits guessing what it could be or join up on vxronline lots or helpful people on there good luck sorting it mate