Most fuel processors take the fuel signal from the ECU and modify it. The way injectors work is they receive a "go" or "no-go" signal from the ECU. The length of the "go" signal determines the fuel amount. If you increase the time of the signal then you increase the fuel. Most bikes are stuffed up by emmissions regulations and are running lean to have a clean burn. Some people will say that this overly lean condition affects drivability and long-term engine life. I have experience with several Cobra PowrPro fuel processors. They adjust themselves via some fancy electronics that measure every power pulse. They are only for big V twin motors. I had them on two VTX1800s and one VTX1300 and they made partial throttle and low speed fueling much better. As far as I know most fuel processors cannot go leaner than the ECM signal. Some fuel processors have a "3D" map that stores additive values for each RPM segment and throttle opening. For example, at 2,000RPM the map might have values for 0, 5, 10, 20, 40, 60, 80 and 100% throttle positions. Computers are fast so this is all transparent to the rider. The Cobras that I used just plugged inline with the fuel injector signal line so there was just two plugs and then a ground wire. Installation was very easy. Other controllers have a lot of wires. I have never installed one of those. Some people send their ECU off to have it flashed. The ECU also contains a "3D" map like a fuel controller. On some ECUs there are restrictions. For example, timing might be retarded in the first few gears and the fuel and/or spark might be retarded at redline. Usually you can get these restrictions removed. The ECU on the R3 is probably very simple compared to fancier bikes. When you open up the bike with intake and exhaust mods you allow more air into the engine. The engine is really just an air pump. So you have a lot of extra air but the stock amount of fuel. The map in the ECU can make minor modifications to the fueling to accommodate altitude changes or humidity/temperature changes, but it cannot accommodate huge changes. So you end up running lean all over. To do all of this properly you need a dyno and an air-fuel ratio meter. This is a very complex topic and what I have just typed should be enough to have a basic understanding. Personally, if I need more power I just buy a bigger bike. I do appreciate precise fueling so on some bikes I have added a fuel controller, but that was just to make the bike nicer to ride. YMMV.