I had the AFC before. My car would sometimes drive good and sometimes shit. My idle would be good one day and then bad another. I also had some kind of missing at 2900 and couldn't adjust the AFC at that rpm so I had to bare with it. As soon as PrimeSpeed installed me the SAFR my car drives like stock. I really do mean it. Mt car idles at a rock steady 900rpms and it doesn't move AT ALL. Considering all the mods I have, its pretty damn respectable. As for power gains, this little gadget gained me 97hp to the wheels by leaning out the fuel curve while the car was strapped on the dyno with an O2 sensor. As for the missing at 2900, they leaned it out for me at that rpm and the problem is now gone :) I also switched to the HKS EVC4 because I now love HKS electronics.
: Opinions on these? need something for tuning after motor is built, wondering if any have found an advantage or disadvantage to one or the other.. Leaning towards the AFC because its been around longer and people know more about it.
