I'm more interested in control than straight MPGs. More point weight on the tires is a very good thing to me.
Lowering the car would also give it a lower center of gravity, and thus better cornering, but there are no lowering springs made for a Tempo. The best I have is a set of variable-rate cargo/control coils from Moog. Can't afford to have them installed right now, though, but I'm going to pair them with new Gabriel Ultra struts when I can. They're the only high-pressure rated struts for a Tempo.
No one really makes good parts for my car.
If I can reduce lift at the same time as reducing drag, that's a mod I'll do. If it creates lift, I'm not going to.
On VGs... Here's my rear roofline, which most likely causes a great deal of separation.. I'll find out later, though, when I do a tuft test. That black strip is raised somewhat, and doesn't allow a smooth flow onto the rear glass.
http://i3.photobucket.com/albums/y93...y/DSCF0908.jpg
http://i3.photobucket.com/albums/y93...y/DSCF0909.jpg
http://i3.photobucket.com/albums/y93...y/DSCF0910.jpg
http://i3.photobucket.com/albums/y93...y/DSCF0911.jpg
http://i3.photobucket.com/albums/y93...y/DSCF0912.jpg