REPLACEMENT FUEL INJECTOR Meets or exceeds original-equipment specifications Improves fuel economy and performance while eliminating hard starts and stalls caused by a worn or clogged injector Manufacturer recommends replacing fuel filter (not included) at the same time. MPI=Multiport Fuel Injection; TBI=Throttle Body Fuel Injection. The VIN number or letter in certain GM applications represents the eighth digit on the VIN.