For some reason i've been having a studdering type issue with my car if it's cold or I dont drive it for a few days. I'll start up the car fine and put it into first and once I press on the gas it seems like there may be a lack of gas going to the engine or something. It'll studder and the RPM's will go down. One time it stalled because of the RPM's went so low. Once I drive it for a bit it seem to work fine. Also, it seems like it donly does this at lower RPM's. Around the 1k - 4k area. Any idea what this might be? Also, I was told by a friend that a puff of black smaoke came the my exhaust while dropping it into a lower gear and acclerating. Thanks!