Not really feasible to switch the connections on the 02's as they are color coded. It is possible to put the front 02 in the rear pipe and vice versa which will throw codes and cause the bike to run strange.

My bike had the cat head pipe swapped for a D&D Boss Fatcat 2-1 early on in it's life and have never had a check engine light. D&D even with the open style of baffle still have adequate back pressure to build great torque.

 

look how close the sensors are in the stock 2011-12 bikes, Pretty sure I saw something in here a while ago about cutting out the cat material and watching a baffle in side the pipe that keeps rear or front exhaust going to the correct sensor, the 2009 are further up the pipes near the heads and wont have this problem, Im sure the vance and hines pipes will solve the problem the original pipes will fit on them, I dont think it is that much of a change to worry about remapping at this point unless you change the air cleaner out also. the o2 sensors should be able to handle the little bit extra flow and adjust the mixtures

 

Update - I went ahead and installed the dresser duals from VH, along with Rinehart 4" slip ons. I also did put a VH powerpak along with a big sucker stage 1 from Arlen Ness. More than I want to spend, but figured I would be done with the exhaust at least. Noticable heat improvement (not as much as I was hoping for) and definite better sound. I'm mean wow, night and day difference... Strange being able to hear EQUAL exhaust noise in my right AND left ear....

As far as the heat goes, summer in FL = lowers come off.....