by controling the duty cycle of the injectors.
with the proper management , EGT gauge , fuel gauge, and o2 sensor monitoring. now it was an expirament but it worked
it would have worked better if we didnt decide to drop it and turbo charge but the ignition was dificult to ajust and use premium gas.
it runs very rich from the factory
one reason is becuase they dont know about every persons driving habits and what brand or uality gas your going to use
so to make CARB happy they stick a precat into the system and a VTCS in the manifold to suppress emmisions.
it was cheaper for them to mass produce these items that really "cover up " the problem because they introdused a old design in the 2.0
trust me i dont think this will be the case in the new cars with the new engine tecnology
i already see the difference in my mazda 6