The thing to understand most manufactures will give you a range to work with and Holley tell leave it where it is OTB.The truth be told this is good advice but Holley and most manufactures don't know your combo and the condition of your engine and your as run or as raced track,weather and all the other conditions that cause changes like altitude and air density.This makes your jetting and adjustments unique to your conditions and your combo.I find many that disagree with my methods but it usually works for me,if I become to confused with carburation calibration I can alway swallow my pride and ask AJ Casini.