I have a weird sound coming from the bottom passenger side of the truck. Initially I thought the truck was misfiring because I had a p0327 and various misfire codes. I've cleared those but the sound still persists. The truck also jerks at speed. If i put the truck in neutral and rev there is now sound and the truck revs smoothly. Lastly, I only seem to hear the sound after driving on the highway. If I'm driving on surface streets there is no sound. Any idea where i should start looking.