The part you are pointing to is the air intake for your engine. This pipe should be coming from the intercooler. Since your engine is a turbo diesel, this would be directly related to why your engine is smoking (assuming you mean it's smoking out the tail pipe). What is happening is if there is a crack in this pipe, your engine is not receiving all of the air pressure it should be receiving from the turbo charger. The engine itself is dumping fuel at the rate at which it would normally (especially if the crack is after the MAF), so not only is all of the fuel going to waste, it also is not getting properly burned. I would venture to assume your power is down quite a bit as well.
Get this pipe replaced as soon as possible and it should clear up your smoking issue.