I took my Fpv f6 ute 330 rkw at soundown race course on a track day event, there were Lamborghini,s Ferrari & Porsche . My fpv nearly munched all of these exotics down the straights 250 km. Since race day my ute now has a slight miss on idle . Replaced the plugs today all electrics check ok , Has anyone have any ideas , vacuum leaks , perhaps valve spring issues , not sure but it runs like dog now after replacing the new plugs. Used nkg iridium plugs . My tuner thinks it might be valve springs there standard from factory .