i dont know much about cars, but i know that im having a big problem. first of all i have an 81 veloce, and when i start it, i usually have to pump the gas repeatedly until the car will start, then, it starts running. then when i take my foot off the gas, it dies almost instantly. also, when i rev the engine, it leaves black marks on my driveway, so im guessing it has something to do with a rich mixture. how do you go about changing the mixture?