2000 Silverado, 1500, 5.3 The truck when in park or neutral the engine sounds to idle regular. When in gear at a stop sign or red light it idles very rough, it seems to be on the brink of shutting off until I accelerate, then the engine runs as advertises. The "Service Engine Soon" light came on Friday last. Didn't have the scanner to read the codes, knowing about my idle problem, I research troubleshooting in my HAYNES AUTO book and learned about removing and cleaning the "Idle Air Control (IAC) Valve", did so and the "Service Engine Soon" light shut off. The engine idles somewhat better, yet rough idle is quite evident. Any Advice or recommendations for a “Garage Mech Wanna-Be”?