Electronic Fuel Injection
Fuel injection is a system for mixing fuel with air in an internal combustion engine. It has become the primary fuel delivery system used in automotive engines, having almost completely replaced carburetors in the late 1980s. In the late 1990s it also began to take over the motorcycle market. But there are still some motorcycles made without it.
Some complaints about fuel injection by motorcyclists include that it is much harder to re-jet or tune up the bikes fuel supply curve after adding new exhausts to the bike. This often requires people to buy a K&N powercommander or similar fuel curve tuning hardware to make the bike run smoothly after an exhaust upgrade.