Well, I came across an old thread that had the DIY version of the XIED resistive device as well as the parts list. about 20 buck in harley part numbers, 6 bucks in heat shrink, and 2 bucks in resistors. The assembly was not for the faint hearted, there's a lot of opportunities for hooking up everything wrong. The best wire to use is the teflon wire inside of ethernet cables. Its the right size to allow all the connector parts to work correctly. So how do they work, barely noticeable....the bike runs a little cooler and the valves / pistons sound just a little more lubricated. I would give then a side thumb only because I spent less than 30 bucks on a set. So if you need a little tweak, this will do it, but you really have to have a pretty good feel for your bike to get a sense of how well they work. It's mainly a low RPM tweak, once you get above 2500 RPMs, the bike starts to run open loop and just remembers the last closed loop fuel ratio. On a hot day, you can get to open look pretty quick.