1997 Chevy Camaro

I have a 1997 z28 Camaro. I just got this car and I had it put in the shop and had a new altinator, new power steering pump and after the mechanic worked on it and backed it out of the shop and it died on him. It would not start back. Once we got it started it was idling really ruff. He found a plug wire cut in two. So we put new AC Delco plugs and wires on it. When you start it up it will idle and run 1000 RPMs then it will drop down to about 500 RPMs and it will die. When you start it back up and go down the road and throw it to the floor it misses out really bad. It has a K & N Cold Air Intake System on it. He hooked it up to a computer and it says that the Mass Flow Air Censor is giving a bad reading. Somthing is flooding the car out. What could cause the car to flood out like that? I drove 38 miles and it used a quarter tank of gas.