FIrst areo mod!
 

Rough template:
http://home.woh.rr.com/slurp812/gb1.jpg


first cardboard total lower grille block:
http://home.woh.rr.com/slurp812/gb2.jpg

Stuff I used to make up the aluminum one:
http://home.woh.rr.com/slurp812/gb3.jpg


Here is the aluminum one on the car, ready for my drive to work tomorrow!:
http://home.woh.rr.com/slurp812/gb4.jpg

With the first cardboard one, it got kinda warm after a short trip, so I went with the small opening. i didn't even measure it yet. It looks to be about 5x7 inches...

That's the same thing I did on mine, blocked off around the plate but left underneath it open. Hasn't been overheating for me but mines not an SI either *shrug*

Did you measure, or notice any difference?

I'll have more concrete data next week as i'm doing the same trip I did this week (without the front covers) with the covers on, I will be doing 65mph for 300 miles cruise control on, the first test got 37.29mpg the drive back with the covers on got me 46.66mpg but that was with reasonably heavy hypermiling (a lot of p&g and drafting)

Well I went from 34's mostly to 37,s mostly. But three things I think are a factor. Grille block, new spark plugs, and its been warmer. Maybe Iv been driving better? There was one tank I got 34 again, but I was on a trip, and in a hurry to get home...