I had the second gen S-afc in my car and I loved it. the first gen is very limited in what you can do. I wouldn't even bother with it. And the original afc is just about useless. It only lets you change the a/f every 1000 rpm or so and thats it. The second gen looks a million times better alows you to view real time data( rpm, Manifold pressure, throttle %, correction %, and one additional channel such as o2 sensor voltage) the second gen also lets you record data. Its pretty sweet. the second gen vafc alows you to choose 8 different rpm points at 500 rpm intervalls and 4 correction maps for High and low throttle high and low cams. I leaned out the bottom end on mine and richened the top end a lil. I noticed alot more low end grunt and the top end power wasn't as patchy and a lil stronger. I also got better gas millage. I tuned it using my butt so I dunno if any of this is for real but I'm satisfied. I bought it because I installed cams. Don't get it unless you have cams or something else that would make the stock fuel map be inaccurate. If you get the V-afc get the fields harness it makes the installation alot easier and cleaner.