Have you A-B-A tested your air dam?
 

This only shows four users and their numbers:
Front air dam - EcoModder

Big Dave, kir_kenix, moorecomp, and wagonman76. Big Dave did not list his cost, but the other three averaged $4. Big Dave used conveyor belt on a truck, so that was a bigger project.

They saw 1-7% improvement, averaging 3.775%, for perhaps thirty minutes of work (Big Dave may have spent longer).

I have a really big air dam, so big that it covers part of my grill! I have not tested it, but wouldn't I need an MPGuino, unless I just do coast-down testing?

I need to figure out the 'guino! :)

Edit!

I thought that the SG and most other gauges were supposed to do well with checking aero mods, but not engine mods where you would want a mpguino.

I didn't a-b-a mine, aside from the amount of work to pull and reinstall, I think the cool down time and changes in weather could have impacted results. I did a lame a-a-b to have a better guess if I should even keep it. Compared to some previous runs it looked like was worth somewhere between 2-4.5%. Think it was about $10 for the paver edging, and another $10 in 1/4" hardware

Big Dave told me about his air dam, so I updated my original post.

I'd like to test mine, but an airdam is best tested on the highway with cruise control and my Kangoo doesn't have cruise. I'm not sure if coast down testing would pick up the difference?

The 96-00 HXes were not available with cruise control, although the next generation had it.

I said that I needed an MPGuino because I have lean burn, although I would expect aerodynamic modifications to make it more difficult to enter LB.

From what I understand, there is a minimum RPM, and wouldn't making your car more efficient reduct the engine load?