I have a modern motorcycle with fuel injection. It runs lean and especially under 4,000 RPM that is annoying because the engine runs rough.
It seem this is a well known problem with modern engines because of emission standards.
Some people use electronics to manipulate what the ECU thinks is the air temperature. I.e. one product (I am not sure if I should name it here) manipulates the air temperature sensor to report about 20 degrees less air temperature. The result is that the ECU adds more fuel to compensate for the cool air so the mixture gets richer and the bike runs smoother. According to the product website it adds about 6% extra fuel and that seems to be the sweet spot.
All this sounds straightforward to me and I don't see any downside except a little extra fuel consumption.
Are there any (expected) problems with things like this?