Bongo Fury

Anybody know what the tube with a non return valve in,that connects the air intake pipe to a "switch" on driver's side just above last two glow plugs does. Just changed the engine and they broke the plastic connector of the pipe and glue has not been very good so far and to add more woes the non return valve has now snapped in half. What doe this pipe do ?

It's connected to the EGR solonoid .Mine broke but repaired it with superglue over a year a go and it still holding strong.I enquired about a new one and there about 30 quid hence I repair it.I'm not trying to teach you to suck eggs here,but you need a quality superglue and you need to clean the surfaces so that they are free from dirt and grease.I think I used locite prescision like I said still holding strong