SAFC is basicaly a piggy back that allows u to change ur air fuel mix eg run more boost and not lean it out amongst other things. Best investment I have made is the PFC. Get a good tunable ecu. I gained 30rwkw from a boost increase to 10psi and a tune on a pretty stock setup, just exhaust FMIC and ecu. Then later when u want more u just add ur mods and retune. Find a good tuner your happy with. See what the tuner does best for your car and do your ur research. Purchase. Tune. Happy Days. If your going to mod later why buy a SAFC to tune then an ecu to tune. Its just an extra expense that you will sell off.