DTC P0304/P0305

2000 Ford Taurus

Engine Mechanical problem
2000 Ford Taurus 6 cyl Front Wheel Drive Automatic 115000 miles

I bought a 2000 Taurus knowing it had an issue. During inspection, the service engine light came on and the car began to miss badly. I looked under the hood for loose wiring or anything obvious and found nothing. I shut off and restarted the car and the code cleared itself and ran smoothly again. During road test, with a cheap code reader attached it happened again so I cycled the key while driving and the code reset and the car began to run smoothly again. I have been able to replicate the symptoms several times and the code will switch between P0304 and P0305. I'm leaning to ward the computer since the code resets itself when the key is cycled. Any other ideas?
November 22, 2009.

Did you check the coil
was it checked for tune up

Nov 22, 2009.