2000 Silverado won't idle.

I have a 2000 Chevy silverado 1500, 5.3 Vortec, 4x4.

It won't idle upon cold start, I have to keep reving it up to 3000-4000 RPMS for a good two or three minutes until the engine is up to temp. Then it runs just as smooth as when I bought it. It has right at 200,000 miles, and has ZERO loss of power. It threw a code for the mass airflow sensor, so I went ahead and did a whole tune up... it has new

Mass Airflow Senesor Coil packs NGK platinum plugs Plug wires Air Filter

The code for Mass Airflow cleared, but now it's throwing a code for o2 sensors. Any ideas?