I have a 2007 Sierra with rough idle. 208k miles. It used to idle at 600, and fluctuate to 450ish every 5 seconds or so. Not sure if I dont have enough pressure , or if I need new plugs or fuel pump.

I CLEANED the throttle body yesterday! Disconnected completely and put it back.

I understand theres a relearn procedure only possible through a code reader/computer...

Please help if you know something.
I can post another video to elaborate anything