car had backfiring problems changed fuel pump and filter fixed that was running like a champ for a while then it got this shake/exhaust seems loud so i changed plugs/wires/coil pack no cheapo sh*t like the guy i bought it off had on it and it runs better but didnt address the problem exhaust still sounds funny/has shake. its driving me nuts because it was running fine then i pull up in the house and an hour later go to mcdonalds and boom its driving funny someone said it might be a clogged injector someone help!!! please!