MyriadPhoenix

iTrader: (7)

Ok i was using the bottle then when i slowed down i had a mis fire, i pulled the plug and the porcilyn was broken but that was it so i figred that i screwed the plug no big deal. i replaced the plug and it is still doing it. i changed the coil pack and also when i drive my car now it sound like i have an exhaust leak. I heard no sounds during use just when i finished the run. if i keep it above 2k it usually does pretty good. Could it be a bent push rod? Broken spring? i have searched through the forums to find the answer but no luck,found people with similar issues but no answers. I read about a leak down test, you will have to forgive me but i don't know what that is. also if i am going to have to pull the head what is the easiest way. any help would be great.
code p0304 is what is coming up.