what is this pipe

[mustydakota]

Got an 85 b2 with 479,000kms on er and she runs strong. have a hole in the cat and the exhaust smells terrible inside the cab and out. Was gunna get the exhaust taken care of tomorrow but i noticed something missing in the engine compartment. Its a pipe that goes to the manifold from the air tube that feeds the air filter. Any ideas of what this is and will it contribute to exhaust smell ??????

Here is a pic with the tube circled and arrowed to which I am talking about

any answers would be appreciated thanks guys

[Ranger Dave]

that thake heat from the exh.manifold and sucks it through the air cleaner so the carb doesnt frost up in the winter