Based on the same EFI system used on the TL1000S V-twin, the GSX-R's single-injector-per-cylinder unit employs a two-stage setup to control fuel flow. At low- to midrange rpm and under light loads, the system calculates injector duration (the allotted time the injector squirts fuel into the intake port) primarily from intake manifold pressure and engine rpm. Since the engine's intake pulses can be very erratic at low rpm cruising speeds, using manifold pressure to measure fuel flow is far more accurate than simply basing it on throttle position. Once the rider starts trying to stretch the throttle cables, however, the system then bases its decisions on data received from a throttle-position sensor and engine rpm. The ECM (engine control module which controls the injection timing, ignition timing and fuel pump operation) not only receives info from the aforementioned sensors, but also checks data from sensors measuring engine coolant temperature, intake air temperature, atmospheric pressure, and crankshaft and camshaft position. Kinda like having Erv Kanemoto riding along with you to keep the engine running sweet. (It appears you can also mount up an aftermarket exhaust with no magic "chips" required).