Not really sure but it sounds like it could be some sort of breather pipe for the crankcase, does it look like it came off somewhere, is it clean inside the end, is it oily looking? You might need to get busy with a mirror and a torch.

 

Thanks Enjay for the suggestion.

There are 2 pipes coming in at the left hand side of the air box; one is the main air intake pipe drawing in air from the atmosphere and the other looks like it is coming from the engine block somewhere - my own guess was a an EGR pipe or a PCV pipe as you suggested.

The "mystery tube", however, is connected up through the underside of the air box into a cylindrical device (about 2.5 cm in diameter, and about 1 cm tall) sitting on the floor of the inside of the air box. The tube is hollow like a straw and is dry inside - my own guess is that air goes through it.

But what is is for and if it needs to be connected at its non-air box side, I am at a loss.

Thanks for your feedback.

Kevin