It was horrible on the fms. Now to be fair it was altered by EB Mods to help out the lackluster bottom end they have. On my modded version the 9853/41005 was really good, 9886/41021 better, losi RE10 was best. These 3 pipes were very close. The 9901 was so bad the fms hit a plateau halfway down the straight and the beauty of that engine is it's topend. If you want some good info on that engine pm me cuz i'm not getting into a pissing match on the forums.