i just recently got misfiring code on all four cylinders. i am assuming that it's spark plug problem since i am using stock plugs for about month and a half with greddy turbo. also i hear lots of bass nose on exhaust when it's idling. like boom, boom, boom. what causes that? i spool up my turbo all the time but never actually go pass vtec. well sometimes i do but i dun go high rpm often usually stays under 5k rpm. any suggestion can help. thanks!