My name is Larry Payne, I have a 2004 Silverado with I believe a Vortec 4.8l v-8. When on a trip at highway speed it starting running rough acting like it was starving for or drowning in fuel. When I kicked it down to pass you couldn't see through the black smoke behind me. It has done this a couple of times now and the code reads P0300 (random misfire). I don't know if this has anything to do with it it but the air conditioning also quit working on the drivers side only which makes absolutely no sense to me. I cancelled the code and it hasn't done it since, around town it seems fine.