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Adjusting the size and placement of bleeds or plugs in the emulsion passages are advanced tuning techniques and are determined by many factors, such as the size of the emulsion passage, the idle feed restrict passage dimension, and the specific gravity of the fuel, and so on. For this reason, most manufacturers determine the fuel flow of the carburetor on a wet bench and then the end user/tuner only needs to modify the jets and low- and high-speed air bleeds. Very rarely do you see a tuner change emulsion hole size or position. The gasoline metering block is red and uses only one plug (looks like a bleed) in the emulsion passages. Note there are four possible locations. The E85 metering block is green and also has a plug, but only three emulsion passages.