While under WOT you will see higher temperatures 1600 isn't surprising at WOT it can also be a lot higher too. However it also depends where the egt sensor is connected on your wrx. If its on the up pipe the temperature reading will read lower than if it was on the exhaust manifold. The exhaust manifold is the proper place for a egt sensor to be located to get the correct readings.
You can also check out this nasioc post Normal EGT's? - NASIOC