tach will be off because the vafc reads actual rpm and the honda tach reads somethign like 800 rpm off i think so ppl dont blow their engines. how much off was the tach fromthe vafc. only thing for vtec is check ur wiring. idk if u wana run an fmu with a vafc. isnt the point of getting a vafc to program ur fuel delivery so that would mean that the blue box and ur setings would try to contradic themself. just what i think.