Hi Doug -
You're doing very nicely with the Tacoma so far. As for "venting" air that enters for cooling, is it not already venting beneath the truck?
Airtabs: I've done a very limited amount of testing which has NOT removed my skepticism that these reduce fuel consumption. See:
Tested: vortex generators (AirTabs) on a Toyota Corolla
If you do a fair amount of highway driving, I'd be looking at constructing an aero shell bed cap - far greater gains to be had from that than anything else at higher speeds.
Welcome to the site!
Darin