OP, if you get and use a O2 wide ban system use the spark plugs and time sheets for the best MPH in the 1/4, use the wide ban to identify where it is lean or fat Most of the stock type carbs I've used and tuned on a dyno or at the track that had wide bans on them show the carbs. going fatter above 5000 RPM Right where the high speed air bleeds can help Do one change at a time on the fuel bleeds and air bleeds, the idle air bleeds can and will affect the entire RPM range as far as AFR are concerned, not just at idle RPM