There is no comparison with running this carb or a factory carb, and the overseas carbs will totally kill your pulling engine. A factory carb starts off good down the track but keeps getting leaner as the weight goes up' That is why engine useally shuts off before tires spin. Just adjusting richer wont help. Our carb is built to keep proper mixture as weight comes up so usually tires break free before engine dies giving you a better pull. Our customers call us all the time to tell us how much better they do. We sell 100 or more of these each year so they have been proven to win. These come preset and (must) be run as shipped. These come in std bore or overbore and our std bore will pass tech as our mods are not tech items.