For me the SAFC works good. I really needed it when I upgraded my intake to an APS one. I had to turn up the fuel because the intake was allowing more air past the MAF. This was on stock injectors. Now I have STI ones and I use it to turn down the fuel at WOT. I do use a Greddy Air/Fuel Sensor and Ecutek Delta Dash for further tuning. If you want in the 12's its best to get it tuned on a dyno. Don't forget you must also address timing!