The guard does reduce your fuel economy, especially if you mostly do highway driving. Removing it should help some (probably not a huge amount). Do you have other accessories stuck to the outside, like racks?

You can find out if 55mph will be a problem by trying it. If you don't find yourself settling in with other 55mph drivers then it's probably not safe to be going at too different a speed from the rest of the traffic. When I am in the mood to go slow on the highway, I generally keep it within 5mph of the speed limit.

I've got side steps and a toolbox that sits down in the bed, but it sits level with the top of the bed.

There's not enough data to say, the box may help or hinder aerodynamically. The side steps are probably worth keeping even if removing them would improve your fuel economy a little bit.

With your commute being so short, your truck probably doesn't warm up until you're almost there. It might be worthwhile to install a block heater.

Does your commute have rolling hills?

Do you drive in backed up traffic, empty roads, or something in-between?

There's your problem... The guns and the rabbit attached to the brush guard. Getting rid of those should help the aero some...

LOL, Just kidding... As long as you're not a speed demon I wouldn't worry about the brush guard.

I know having a third car is pushing it, but you could get a cheap used vehicle that had greater efficiency. Used car wouldn't need too much in the way of insurance and multiple car rates for liability are usually low. Or maybe a scooter or motorcycle, if your area and inclinations lend themselves to one.

With his short commute, an additional FE car for the commute would never pay for itself unless it was free and the insurance on it was free.

I heard that if I cut off my catalytic converters my engine would run more efficient and get better mileage. I've got BFG All-Terrain tires on it right now, are those good for rolling resistance?

Getting a 3rd car probably won't work since I already have 3, Truck, corvette and a mustang. I dont need a 4th car.

Cat coverters might restrict flow a tiny amount at redline, but considering fuel economy alone, there is no reason to remove it.

I do not recommend removing the cat. What will happen is that the computer will sense this, assume something is wrong with the system, turn on the check engine light, and run in "limp home" mode on a set of preset parameters. Your mileage will likely go down.

The tires are another thing. You may see a gain going to a tire with a less aggressive tread. I have highway truck tires on my K1500, and its performance off road and in snow & ice really hasn't suffered much. If the tires are due for replacement you may see a gain from tire replacement. Unless you have a really aggressive off road tread on your tires, or you have super swampers on it. Otherwise the expense of the new tires probably won't pay for themselves.

just a thought...

assuming you NEED a truck, would you consider a 4cyl model. that a manual tranny could help immensely!