Originally posted by HybriDSM Don't tune by "popping sound". Get a datalogger at the very least and tune with knock counts. Doing it any other way is just guess work. Set the Low to 20% and hi to 80% and tune super rich and back it down til' your 02's are under control but you are still not knocking (well a count here or there is passable but not recommended). The setting for hi are the important ones as those represent the settings that are default at WOT and close to full throttle. 20% setting are those that exist when the car is idling and having barely any gas applied. All throttle positions in between are computed by taking the mathematical average of 20 and 80 for any given throttle percentage. This means, at exactly 50% throttle, the car will take 20 and 80 and average them out. Knock means lean means bad means give more fuel before you melt piston.