[lunarhighway]

as mentioned above, block the upper grill, the angle of the resulting surface looks vavorable, you could also build small dams in front of the front and maybe rear tires,
based on comparisons of oem dams the ground clearance of the dam should be about 1/6 the tire height. oem dams often don't span the entire width of the tire but do follow the curve of the inner wheel well,

an undertray under the bumper and as far back as you can is also a good idea.

deleting mudflaps might also help if you can live without them... i this seemed to help on my previous car.

the most gains are to be had at the back though, but it'll be dificult to achieve

if the trunklid edge is rounded a small lip spoiler that basically straightens it might help, no fake wing spoiler though.

same thing goes for the underside of the rear bumper where an undertray might also have a good effect. fill in the large gaps or cover everything with a sheet.

i wouldn't worry about the moldings of the side (the front weel wells have messed up the flow already), or the fog lights (take a look at the new prius for example, they seem to have deliberately added a more blocky edge, so the fog lights might actually help aero!)

the last thing i can think off is next time you get new whipers is get some low profile flat blades... i'm quite happy with these and they do sit a little lower... whipers don't affect airflow very much, but it's still an easy mod to do