If you want a cleaner, smoother sounding exhaust, install an X pipe. What kind of balance pipe are you running? W/O one will really give it that "mustang/cmaro" style note that your referring to. Personally I cant stand flow masters.. they always sound too raspy but this is a personal preference. If you want a nice mellow note w/ solid bass... swap (2) quality 2.5" canister mufflers like HKS, Blitz, tanabe, JIC etc. If thats too much dB for you, try running the provided silencers or swap over to magnaflows... I have them on both of my rides w/o any hint of raspiness or droning.
Any pics of the new system?