Rough idle on stock 2001 silverado

I just purchased a 2001 silverado, and I detect a slightly rough idle stopped at a stop light, and a slight hesitation on take off. It doesn't effect the performance much, it just causes a slight feeling of apprehension... Does anyone know what might be causing this.. btw I just had the master air flow senser replaced.

1. replace fuel filter
2. have the fuel injectors cleaned.
3. clean the PVC valve
4. B-12 the trottle body
5. replace the air filter

What rpm does it idle at? If should be at 600 for gas.
I have mine at 500. It is a little rough.