I recently purchased a 1995 Miata and it seems to run fine except for a slight hesitancy when accelerating at lower speeds. I was driving the car up a hill and the engine light came on. I checked the gas cap, which was on correctly (and I heard some gas escape when I unscrewed it). I turned the car off and went to a store and then about 20 minutes later drove down the hill and back home and the engine light did not come on again.

I checked the oil and it was OK.

Any thoughts?