This is apparently some sort of vacuum tee. The larger end goes to a port in the plenum. One small end to the vacuum line that apparently opperates the a/c ducts. The other smaller one goes to I believe the cruise control gear. This looks to be some special design and does not run straight through on in inside. I know this because you cannot see straight through where the holes line up.

Can someone tell me if there is something special about this "vacuum tee"? Why this design?

Thanks.

 

Ive always wondered the same thing. It is what you say it is cause thats the same way mine is routed. Can you blow thru it?

 

Looks like a tee with a check valve to keep the blend doors from constantly opening and closing due to acceleration. NAPA sells them.

 

you can blow through it in all three directions and you can suck air from all three also. I was trying to see if it was some sort of valve. there's got to a reason for the this design. Maybe I will cut it open to look inside.

 

Got it. Went to a parts store and confirmed it is a "vacuum check valve". AC Delco part# 14056648. I put it in, and my a/c vent doors don't activate anymore on engine start up. All works perfect now.