Apex VAFC is ok for a pretty stock car. if you have lots of mods, or a considerable amount of bolt ons, it sucks. VAFC/SAFC alter the signal to the map sensor to let you control fuel. this is why if you have a VAFC and you add +20 fuel it will throw a map code, cause it thinks its seeing boost. Adversly it will retard or advance your timing when adding or leaning out fuel. VAFC/SAFC only control FUEL, not timing

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