Hey Scotty, 

I have a 1999 Chevy Silverado with 347,500 miles on it. It has the 5.3L V8 in it. For a couple months now, I have noticed a high idle after the engine warms up and has been ran for a while. It did not do it everytime I used the vehicle, but 1/3 of the time, I had the issue pop up, no CEL codes.

Fast forward to last Saturday (2/18), I drove the truck about 35 miles to work, I got to the gate at work and came to a stop, the engine started running rough/sluggish for about 3 seconds and then smoothed out after I inched forward. It ran fine the rest of the day. 

Today (2/20), I was sitting in the drive thru at culvers with the engine off, but warm. I started my truck and it revved a little high on start up, the proceeded to run sluggish for, again, about 3 seconds. I put it in gear and inched forward and it smoothed out again and has ran fine since. 

What could be causing these random and short sluggish moments? Could the high idle be related too? I would think that they are but I'm not an expert. The truck runs really great overall outside of a few small things, so I'm really perplexed with this issue. Thanks Scotty or whoever else answers!