Great find, couple of us were just talking about this the other day. I read the link and found this interesting, "I wanted to confirm that STi LED+heated mirrors will bolt right up to a 2011 WRX Premium without modification.
My guess is at the least 2011+ WRX Premium/Limited come pre-wired for led turn signals since they they come with heated mirrors already. Just a hunch.
It took nothing more than unbolting my old WRX mirrors and bolting on the STi mirrors. LED, Heat and mirror controls all work.
I bought the mirrors whole off a wrecked STi. I did not piece them together." . So it appears Limited/Premium owners can just do this as a "bolt on". What do you guys think of this?