2000 Chevy Malibu, 110k. it shakes while it is idling and when i'm coming to a stop, and when I park it, it has a burning smell coming from under the hood? Also gas smell from the tailpipe. The check engine light is not on. But I have had a p0341 and p0300 code in the past. While i'm driving it has a loud rumbling noise to it.