Kerker makes great slip-ons. If you're tuning your EFI the Mikuni baffles flow best, but they sell 10X more of their SE slip-ons. All less than $350...
I got the rush slip ons 2 inch baffles today. For my 09 ultra. 15 minute install. If you want harley sound but want to hear radio these work great. great low tone.