I have seen a few rigs (evil chevys) with these ram air things that look like a dryer hose hooked to the air cleaner, and aimed out the grill. Do these do any good?

 

they only do any good on the highway or at the 1/4 mile. in real world stop light to stop light draging they do very little, and sometimes hurt bottom end(as it did on my 89 thunderbird, but it picked up top end on the highway after 55mph quite a bit)

if you take the truck off the road in mud or severe dust forget it though.(water likes to go straight up these)

 

I think it would be worth a try, I think banks sells them, but who else sells one, anybody know?

 

I built one for my 460 powered motorhome. I like to think it helped but at 6-7 mpg, who knows! It stands to reason that if you are getting a more dense, cooler, air from outside the engine compartment it should help. I would think that the frontal air pressure at road speed would be better than suction under the hood. Gale Banks engineering sells a bunch of them.