Go to a big money race and ask around, Rupert will be 2 to 1 over ant other alcohol carb there. VERY, VERY CONSISTENT! A lean out valve is not part of the carb it is an add on you do not need it! I use it if i need to warm the engine up quickly or if it is cold outside. I have not seen one brand over the other that is good for a tenth if both carbs are jetted the same and tuned correctly. Just my opinion!