Will a better air box intake and a free flowing exhaust help gas mileage at all ? or is it not enough to even do it....

 

V8, V10, or diesel?

V8, V10 - probably not enough to notice.

diesel - exhaust, yes

 

Agreed.

The gassers are not getting poor (relative) mileage because the engine has to work too hard to suck in and blow out. (Pumping loss)

 

Sorry. V10...

 

Both gassers have nearly identical intakes and those intakes are already cold air intakes. If there is a small "issue" with them it may be the nearly 90* bend the intake tube takes.

Opening either end will give a few more ponies up top and a bit more noise. Don't expect those mods to improve MPG to any degree.

 

I pull a steady 14 on the highway at just below 65, and that's turning 37's and 4" of lift. I've got the K&N CAI, Jet Throttle Body Spacer, Superchips Tuner, and nothing behind the cat.

Every vehicle I have ever owned its made a difference on, but least most of all on the ex., I'm assuming it's because of the size.