1990 Hyundai Excel sputtering-bucking

I have an 1990 huundai excel with 72,000 miles (original) and in the past few weeks I have noticed a conciderable problem, basically, I have replaced plugs, wires, and most of the electrical system, I have noticed the car wants to sputter and/ or buck, and its not just at one particular time, it doesnt seem to matter, when its just started, running for a while, at a light, or what have you, could this be due to the MAF (mass overflow sensor) if so, where would this sensor be located?