The term “full bolt ons” for the WRX usually means an intake, downpipe, headers, intercooler, tuning, and electronic boost control solenoid (EBCS). You might also hear the terms stage 1-3 to refer to mods. For the FA series, stage 1 is generally an intake and a tune; stage 2 is a downpipe and a tune; and stage 3 is a downpipe, tune, intake, EBCS, and intercooler. The EJ255 is the same for stages 1-2, but stage 3 is a tune, intake, downpipe, EBCS, fuel injectors, fuel pump, and fuel pressure regulator.