MyTwoChevys

I did not think to take a picture of it.

I had this same noise. I tied off my flapper valve and that made no difference. I put my truck up on a rack and was looking for anything that could be causing this noise. It sounded like it was coming from just left of center of the dash from the inside. I found that the drivers side of the engine the ignition coil cover was off and was down and wedged between the steering shaft and the engine. And it is not like it could just fall off. It has a crankcase vent line that goes through it when it is installed in its correct place. So it had to have been there from the factory. Maybe they tried to install it without pulling the vent line out and that caused it to come off over time. I put it back where it belonged and the noise went away.