alright so this has been happening for a while and i have to get my emmissions done so i kinda wana prepare myself it doesnt pass. I think my car may be running rich, atleast thats what my dad's opinion is. He commented how he thought it was running rich because of the excess exhaust build up on my back bumper about the exhaust. Could this be true and a sign that it is? if it is, then what may be some causes of this to be happening.