2006 Hyuandi Sonata GLS V6 3.3 Liter – 92+k miles. While driving the car yesterday, it just shut off. I saw & smelled some smoke come through the heating vents. Upon opening the hood, dead center directly in front of the bumper, there is a 3-4 in wide by 5-6 in deep round cylinder type part that looks like it connects to the exhaust was smoking. The car starts but has some type of rattling sound now. Just had the oil changed 10 days ago at Hyuandi dealership along with full service check, found no problems. There are no service lights on either. Any ideas about what it could be and how much it may cost me to repair it?