Originally Posted by chud

I think that piece you're talking about is just called a vacuum check valve. It keeps the vacuum flowing in one direction. I took mine off and blew and sucked air through it this weekend like you said.

One thing on mine is when I lift up on the air filter assembly, the engine starts stumbling and stalls just like it does at idle sometimes. I don't think it should do that. Does yours do that to? Could somebody whose truck is running good tell me if theirs stalls when you lift up a little on the air filter plastic assembly? I don't even take the wingnuts off the top - just give it a little upward pressure and it starts running terribly and eventually stalls.