krenogin

Hey, first timer here. I have an 02 mustang v6, has been minorly wrecked twice. After awhile it started running bad around 70k miles, i have put new plugs in it, Bosch Platinum +2's and it seems to have made it worse, i did not change my spark plug wires. i have a K&N airfilter, hasnt been cleaned in awhile, it is bone stock, was tuned but got reset after batter change. At idle it is smooth then out of nowhere a big vibration, and goes smooth, just contiunally does that. When i rev the engine it revs fine then when i let off the gas it seems to wanna backfire very quietly, its very odd. I recently changed the fuel filter too, and ran lucas engine cleaner in it. Help please! The miss is agervating and seems like my fuel mileage has went down.