Not on a truck with big tires.

 

The exhaust opens up your top end. Stock exhaust helps your bottom end. The problem is your truck is a heavy pig and it is hard to get it moving. You need more low end power to get it rolling which will help your mpgs.

Might consider a small duration cam.

 

Re-gearing to 4.10s will help mileage as well.

Less work to get the truck rolling...

 

Re-gearing to 4.10's will help mileage??

 

It will with a lift and bigger tires.

 

Brick mod behind pedal

 

Would I notice going from 3.73s to 4.10s more power and better mpg?

 

More multiplied axle torque? Yes. Better highway MPG? No. not without lowering the 4th gear (overdriven gear) ratio in your transmission.

 

How so?

If the motor doesn't have to work as hard, it's not going to have to use as much fuel...

Is he going to get back to stock mileage? Not likely... But it will get better, even on the highway.

The right gearing will bring the RPM's back down on the highway, the trans will last longer, since it won't always be changing gears to turn the heavier wheels and tires...

Though, it's not likely to be worth the money to DO the gear change vs. fuel savings...