Yukon XL Rough Idle

I have an 02 Yukon XL 5.3 with 209k mi. The truck starts fine and runs fine until it gets warmed up. Once it's warm it idles at a steady 500 rpm, but is very "rough", lots of vibration. I've cleaned the throttle body and MAF, but it has not helped. The engine is not throwing any codes. Turning on the AC makes it much worse. Any suggestions as to where to look next?

Welcome to AF, if it is matter of the idle too low this is one issue, if it is an actual misfire this is another, many factors can cause what you describe. A vacuum leak is one , a lazy or carboned up idle air control is another.