I have experimented with the ViED's (adjustable XiED),on my 2012 Cross Roads, running less restrictive mufflers and 4 degrees injector and spark advance. I think the gas mileage was close to same, maybe a few mpg better than without ViED. Here's the thing with the Vic, the ViED will trigger a Check Engine Light during every warm up, start and restart. The low voltage is out of range until the o2 sensors see some heat. On a HD when that happens it stores a code, on Vic you get CEL. The other more important difference on a Vic, is that you can simply disconnect the o2 sensors with no CEL at all. This will achieve slightly richer results than what is possible with the ViED's according to dyno runs at crusie done by Rylan. If you could disconnect the sensors on a HD like you can on a Vic, the XiEd, ViED, would never have been invented.
2013 Honda F6B
1951 Harley Davidson HydraGlide