Mine made immediately measurable gains (SG1) of about 3% @ 95 km/h @ 2C. http://www.metrompg.com/posts/grille...ing-part-2.htm . If you're not directly measuring with instrumentation, the effect will likely be hidden in tank-to-tank variability.
I finally made my "good" version (after at least 4 cardboard & duct tape versions) last weekend: a custom "bra" - helps keep the bugs off too! I'll post a pic eventually.
I'm really wishing that I had a manual tranny in mine. When we bought it new we were living in Chicago, and an automatic made more sense there (or so my wife said :-) ).
Linear Mode
