Recently started running rough and misfiring when cold?

I have a 1999 Tahoe that recently started running rough and misfiring when cold. This problem goes away after about 10 miles of driving. The car idles well at all times, misfires under light throttle application, but goes away under heavy acceleration.
The car has been tuned up with new plugs, wires, distributor cap and rotor, and new fuel filter. The engine light is on and only one code is present: "Random Cylinder Misfire" (I don't remember the code number).

It seems like a fuel related problem to me, however, I am wondering about oxygen sensors, or possibly the Mass Airflow Sensor. Any ideas which direction I should go would be greatly appreciated.

Thanks!