To achieve optimal performance using the stock carburetor, we offer DYNOJET carburetor jet kits. In combination with K&N replacement air filter and individual air filter ( Order No.: 50-3713 ) ( Order No.: 50-3713), up to 5% higher performance can be achieved. The scope of delivery includes softer slide springs, modified jet needles and several nozzle kits. STAGE 1: For standard or slightly tuned engines with standard exhaust or TÜV exhaust. K&N replacement air filter in the original air filter box should be used. STAGE 3: For light or medium tuned engines with open sport exhaust systems and K&N single air filters ( Order-No.: 50-3713 ) ( Order-No.: 50-3713 ).