RvFNG76:
TBI -- Throttle Body Injection, one injector in the throttle body. The computer that comes with aftermarket units has to 'average' the eight cylinder when tuning and adjusting the injector.
MPI -- Multi-Port Injection, eight injectors, one in each of the intake manifold runners. The computer that comes with aftermarket units can tune and adjust each injector for the cylinder it serves.
Don't ask how the computers do that unless you want a PhD level course in software engineering and computer programming.
