i have been noticing at night, when sitting at a redlight, smoke coming from the back of my truck. the only way i can see it is if a car is behind me, and i can see it with their headlights. my truck has about 8600 miles on it now, but i noticed this since day 1. i thought it was just breaking in or something. but the truck has plenty of power so what gives? is anyone else seen this or heard of it? should i take it to the dealer and let them look at it? Thank you in advance!