engine hesitates..

i just bought a 92 mr2 n/a , 5spd, t-tops, 162k, and when im accelerating it hesitates alot, and is really noticable, the car surges froward almost sometimes, and i dont know what it is, someone told me to get some fuel system cleaner that you put in your gas tank, well 2 tanks later and it isnt any better, the air filter is brand new. i was thinking mabey its the spark plugs so im gonna change those out soon, any other ideas? thanks

Every time I buy a used car I immediately do ignition components: cap, rotor, wires and plugs.
I would suggest you do all of them as well ;)