I think the urea injection also helps with the mpg and hp. That way they can increase timing and engine hp without having to worry about how much NOx is produced in the cylinders. They'll let the urea clean it up in the exhaust. Just a thought, I haven't done research on it.

 

The second video sounds like a plugged muffler with a blown intercooler

 

If you let the urea tank go empty it will go into a limp mode state, but will give you tons of warning before it goes empty. Just as a side note.......