[puddleglum]

Congrats on the mileage improvement, great job. I doubt washing the car had much to do with the improvement though. From what I've read, any improvement from wax is too minimal to even be detectable. OTOH, the grill block and sealing the seams probably helped quite a bit. Your driving is probably improving as well, maybe more than you realize.

If you travel on the highway lots, I would suggest building a belly pan. I've never tried a WAI. I was going to but people here have said they are not very effective with a MAF sensor like on our cars. They work best with MAP sensors in older cars.