Idle Speed on Tahoe

What is the common idle speed for a 2000 chevrolet tahoe 5.3? I have one that is idling around 500. When it starts it drops down to 300 and jumps back up to about 500. I don't think this is normal, but you all let me know if it is. Thanks a lot for your help.

My 2000 Yukon idles around 500 but does not drop to 300. I have heard that you should clean the TB when this happens.

//2000CAYukon