2002 Chevy Cavalier I think my car is dying.

I recently purchased a car which has been sitting around for over a year. The car was started and ran only once or twice during that time. The car would not start at first and we had the fuel pump, fuel filter, plugs, and wires replaced. The car now starts, but stutters when you hit the accelerator. As you go through the gears it sputters a second or two before accelerating again. It is also sometimes difficult to maintain a certain speed without the car sputtering or lagging. The car has also begun to let out excess blue or grey smoke from the exhaust, especially when idleing or when first started. I now turn the car off at lights to not annoy people. Car runs better at imes where there is almost no vibrations and smooth acceleration, at other times I think the car may blow up. I really need this car for my wifes sake, if anyone can help, thank you.