I was trying to pass smog today and after the test, the guy there brought to my attention this hose swelling up.
It's never done that before. Any ideas on what's causing this?

Also, coming within only 1 point away from failing the emissions test,
What are some of the most major things that cause unburnt fuel?

See photo!
Thanks,

-Mark

 

the things that cause unburnt fuel is timing.

 

replace the hose

 

The hose needs to be replaced ASAP. Make sure it doesn't swell up again with the new hose, because that means you have a clog in front of the hose itself.. For the smog... Do you have new(ish) spark plugs? Highest octane gas possible? get the car hot so your catalytic converter works better. Change your oil, make sure your air filter is clean, timing is VERY important, as hybridmiklo said.