To the OP, unless you are really in love with the dual headpipe, I think you would do better by switching to a 2-1-2. I know everyone is fond of Fullsac, but the stock catless headpipe is a great performer, and you could find one cheap.
That, plus a good tuner who could make it run nice with little or no power loss. Best is to ask the tuner's opinion though- he would know best.
As far as the tuners discussion, I find it surprising Brian doesn't use the SEPST, since he does his work at Harley dealer. Dave Stoddart I would believe, because he specializes in the TTS when he had his own shop, so the fact he now tunes out of an HD dealer wouldn't mean he would use the HD tuner. For me, I own both the TTS and the SEPST, so I could go to either, but Brian is closer and I'd feel better having a SEPST tune because if I ever needed it tweaked later, I know local tuners that could do that. No local tuners use the TTS though.