If I went with Fullsac X pipe and cores to go along with Andrews 57 cams what size core would you think would allow it to breathe the best and listen to the radio at cruise 2.25 or 2"?
Generally speaking, the 2" cores give the best overall performance, but the differences are small. It mostly comes down to a subjective call on how loud you want the bike to be. The 2" cores, for me, are PLENTY loud. I personally would not want anything louder. Keep in mind that whatever mufflers you get, they are going to get somewhat louder over time, as the packing burns away. With the cores, you can pull them back out and repack when needed. From my understanding, the Fullsac "C" pipe is really designed for engines larger than the 110. If you plan on bigger mods to the engine than just a cam swap, that would be a consideration. Steve at Fullsac could advise you on that choice.
There are other good exhaust systems out there, no doubt. In a nutshell, here are the advantages to the Fullsac Stage I system (even with the cam you are choosing): It's a proven system; They provide great customer support; If you like the look of the stock exhaust, it maintains that look while utilizing the stock heat shields ($$$ saved); The installation is simple/easy...if you own basic tools and can operate a Dremel tool (or equivalent) and a laptop, you can do the install yourself in 3-4 hours maximum; The TTS Mastertune, IMO, is about as good as it gets for a HD motorcycle; The system is virtually "plug and play"; If you do the work yourself, the cost is < $1100 for everything. The cam swap you are talking about would be the only variable that would add to the cost and would probably require a trip to a good tuner to have it all dialed in precisely.
The ECM map provided by Fullsac is so close, you likely won't need to rush to a dyno tuner to have it tweaked. I'm still running the canned map provided to me by Steve, and my bike runs just fine. It could probably benefit to some small degree by having a good tuner tweak things a bit, but finding a good tuner is another challenge, depending on your location. If you live near Florida or Northern California, that's not an issue.