I have a 2011 WRX 18500 miles. It has been high idleing around 1500 rpms when first started and as it warms up the rpms slowly drop to about 800 rpms. The car drives fine and I do not have any error codes. Once it is warm the high idle goes away even when the car is turned off and turned back on. BTW it is hot as $%*@ where I am located.