Help with odd occasional odd noise

[02x72]

So a few months ago I was moving up to ND, pulling my fifth wheel, around 10k lbs, and twice on the trip I would get a very odd, and scary sound from the engine. The only way I can describe it is like an excessive rocker noise on a gasser, like if they were loose, but louder. Ive pulled the valve covers, both before and after the incident and all seems well. It did it both times on fairly flat ground, not on the hills where she was really working. After the second time the truck had a significant power loss, but it went away after 40 miles or so. Hasn't done it since, but the thought of pulling the 5'er any great distance after that kinda worries me. Any idea what it could be?

 

[jwalterus]

air intrusion maybe? I dunno, where'd you move to up here?

 

[02x72]

Im currently living over in Sidney, Mt working, but work all between here and Williston. Doubt the air intrusion, I eliminated all of that before I came up here. Guess theres no guesses, I'll just go on hoping nothing blows up

 

[6.9man]

best bet check compression and if that's not low be fuel related issue. welcome to nd good to see another idi man around