If you installed the power duals and new mufflers without a tuning device of any type then surely the bike is running way to lean and therefore way to hot. As you state you're not new to this game and no offence meant but you probably know better than to change mufflers and headpipes without a tuner - the ECM can only make adjustments for minor changes (like maybe different slip-on mufflers) and changing the headpipe and removing the cat is not within the realm of minor changes.
Also just by changing the head pipe and removing the cat you have potentially jeopardized the factory warranty -- depending on the dealers' relationship with you.
But as to them not wanting to install a tuner is IMHO total BS on their part - did that statement from them also include HD creamin' Eagle tuning devices? I think a visit to one of those other dealers that will install the tuning device of your choice is advisable at this point. I would personally stay away from any "piggyback" type units , and my personal choice was the TTS (I also went with the Fullsac stage 1 treatment on my '11 CUSE6).
As to cost, well the cost of the bike was just the cost of admission to the HD fun park.
Sorry couldn't resist that last line