Losing throttle response

OK. I am lost! about once a week my 05 Columbia (14L Detroit) will be pulling fine then if starts losing power. The check engine light comes on but when I let up on the throttle the light goes out. No codes. Sometimes shutting it off for awhile it seems to run fine again, or in this latest case it bogged down to about 20 mph, then suddenly picked up and ran fine the rest of the night. I am at a loss. I suspect its an electrical gremlin. Any thoughts would be great.

 

In other words you are saying the turbo might be choking the engine. Any idea how to check? That's an expensive part just to throw the problem.

 

The bill says the following...Current code for VNT vanes not responding - could be from low air at start-up. Found actuator leaking. Tested CAC - ok. Dynoed truck - Pulls at full power and reaches full speed.
I should have made them check the truck before they shut it off when I dropped it off. It came in acting up. But as I said before, when you let it sit awhile or overnight, it runs fine till the next episode.