You will be able to notice alittle power increase and yes it will have to be jetted.
i jus got a hmf for my 450 i can deffanitly tell a difference in power and if u buy a hmf it comes with a jet and after u install it it will still run a little off so u will hav to mess with the air/fuel misture screw and the idol to get it rite .good luck!!You will be able to notice alittle power increase and yes it will have to be jetted.