Idk about comparible to an fmf.. Theres a reason ppl pay big bucks for these pipes and fmf is cheaper!! These pipes need to match the porting and polish of the cylinder, compression, carb, airflow, jetting.. All that stuff comes into play to make the bike work correctly.. Ice racer can say some more about all this but honestly he has the numbers to show on the diff pipes and what not.. Everybody has opinion and idk if i trust ppls seat of the pants dyno suggestions.. Everybody likes a diff set up.. Me i like snappy!! I want the bike to flip over when im on the throttle but others dont.. If the ftz is topend pipe then idk if ima want one of those.. I want the low-mid for trails!!