when they were testing the trucks in the desert, they were to the point of overheating, so they made them smaller for better cooling. then they eliminated them all together.
Mines an 04 and came with the little one.
I replaced mine:
with out it, you do end up getting a ton of crap into your engine compartment, after putting the new one on, plus the front skid plate, I dont get hardly anything into my engine compartment. Which is why, my engine is so clean all the time.