Do you have coil packs or a distributor that the wires from the spark plugs hook up to? If it's coil packs, and one is bad, it could causing a misfire, or a whole cylinder to be down. Meaning you would be way down on power. Computer diagnostic from Autozone might help, but you can test it by running the car and unplug one wire, with the other three in, to see if you have a dip in power. If you get a dip in power, then that one is fine. If you unplug one, and there's no change, you've found the one that's bad. Try this with each one, and if you get a dip with each, you can most likely rule your ignition system out. Other thing I can think of it the TPS sensor, or the throttle position sensor. A computer diagnostic should tell you if that's bad too. So if you've got a check engine light on, start with the codes.