DevilzTower is right -- turbocharged and intercooled.
Duffman -- it's probably 70% city driving. That's one reason I have focused more on driving style than aero mods so far. I'll probably move into aero stuff soon, but I still want to stay fairly conservative.
oil pan -- I would love to find some slightly taller tires to change the overall gearing a little, but it's tough to get taller without getting any wider. Stock tires are 235/85/16.
The truck is a regular cab long bed, so an aero cap would probably work really well for highway mileage. I'm a mechanical engineer by trade, so I've got some good software to play around with. I mostly do Finite Element Analysis, but I have done some CFD and have started up modeling a pretty rough truck with which to run some basic flow simulation. Mostly, I'm curious to see how a small "kammback" for the cab in conjunction with a partial bed cover will compare to a full aero shell.
I also would like to do some underbody work with an air dam, since I don't want to go any lower than the stock 2wd truck sits. I've also got a few ideas for the wheel wells, since I don't really want to run covers. I have tossed around the idea of doing an intake -- I don't think that it will help fuel efficiency much since the air flow rate is so low under those conditions, but I wouldn't mind hearing the turbo some more at a lower load/RPM
