It is an upgrade. If you have a 1977 carburetor speed kit for the stock 14.14 PHVA, it comes with a different emulsion tube, main jet, and idle jet. This emulsion tube is a little bigger than the stock one. Look at the numbers if you don't believe me. The stock one is a 209GA and the 1977 emulsion tube is a 210GA. Like what sabat said, the tiny holes allow the fuel to mix with air, making the gas easier to "emulsify" or "atomize" when going through the carb.