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.
FYI, the blinkers were on in the photos. I was good with timing the photos. Neither the mirrors nor front turn signals have running lights.
STi on the left / WRX on the right
STi harness plug
WRX harness plug
Door harness plug
I hope this helps somebody.