Speedo Correction
 

I think our speedometer reads high from the factory but I went with some undersized tires so my speedo is probably off by quite a large margin. Is there a way to re-calibrate the speedo?

I would recommend taking a look at the Yellow Box Speedo Recalibrator (www.yellr.com). The company that makes it is based out of Australia, and I used an earlier version of this device in a 2003 Toyota Tundra. With a GPS unit, I was able to verify that it worked flawlessly in that application. For our twins, I suspect that you'd probably need to splice into the "SPD" signal wire found in the wiring diagrams (pink with a green stripe, at least in my particular copy of that diagram).

It's been several months since I've run the EcuTek Pro ECU software, but I believe there are some settings in there to correct for over or under sized tires.

That would mean you would need an EcuTek tune.....

.....But, there may be some settings in the Techstream (or Subarus equivalent) diagnostic software that the dealers use to perform those adjustments. I'm sure someone here who is more familiar with Techstream will chime in to verify.