I had a shop recommend pipes for a Dyna. I trusted them and told them to choose the best fit. The headers ended up sitting so far removed from the top end that the shop (rather than not installing the pipes), extended the break peg. So I rode home that day with my right foot out twice as far from the bike frame as my left....it was awkward. Pulled into my garage and took the pipes off immediately. Found a great pipe system that fits like a glove......and now have an expensive Dyna designed pipe system with 25 miles on it collecting dust in the garage.
Two reputable pipe manufactures for your FXR:
Thunderheader......tried and true.
RB Racing.............high performance.