Rotaries like seafoam! However, lots of carbon could prove detrimental to seafoam cleaning as it would break aprt the carbon and cause issues internally (loss of compression due to removal of carbon + worn out old engine). However its the only "internal cleaner" i would run through the fuel system. If you actually want your injectors clean, Kirk at boost lab in Temple Terrace will clean, rebuild em, and flow test em for you. Thats who does all my injector work.