While prowling around the back of the engine I found this. On my engine (4.2), it was a 3" plastic tube running running from the left side of the throttle body elbow to the Supercharger Bypass Actuator (also on the left side). As you can see, it is almost completely collapsed. I replaced it with some normal rubber vacuum line.

Be careful removing it. I was afraid of breaking the rubber elbow (quite hardened) and the connector that connected it to the tube. I chose to pull the tube and connector from the rubber elbow. I swapped the connector into the new hose and plugged it all in.

BTW: The tube's part # is: AJ83877. God only knows what its list price is - lol