Dynojet Jet Kit 4175 Average horsepower increases of 15%-25%! Each DynoJet kit is precisely engineered to provide a simple and cost effective solution for all your riding needs Kit includes jets, needle, spring, shim and instructions Stage 1: stock engine/filters, stock/modified pipes; about a 5% power increase Stage 2: stock/mild modified engine, stock/ modified pipes, stock/modified filters; about an 8% power increase