Does it work = probably....20% gain of both fuel economy and HP = dreamland....
Can't have both at the same time. You either richen up the mixture to get more power or lean it out to get better fuel economy. You are not going to gain any more MPG then stock without running too lean and too hot.
Better options on the market with tuneability. Looks like just another piggyback modifier to me. There are much better options on the market for a cheaper price. I personally like and run OSB.