The EPA rules and warranty issues probably does have a bit of a impact but the better question is do you really need to tune any of the other brands? The other manufactures may be under the same EPA issues but they are doing a VERY good job of making sure the meet the requirements as well as producing a motor that doesn't require "fiddling" to make it run right.
Which circles around to what we talk about all the time, build specs and quality control. Are these other brands plagued with sumping, crank run-out issues, lifter issues and so on? I think not.
It looks like poor sales are being driven by several possible issues:
Buyers lacking disposable income due to their ACA payments in spite of a good trickle down economy. (debatable)
HD Design flaws and poor quality control that drive buyers to other brands. (verified)
A MoCo sales system that punishes dealers who can't move inventory giving them incentive to sell to unqualified buyers. (apparent)
An aging out market leaving a vacuum not filled by the next generation. (generalized)
Of all of those, the only ones the MoCo has any control over is design and quality control, and sales tactics.
Not holding my breath on this.