That's why I double-checked to make sure we were talking about a "mostly stock WRX" before I referred him to the article I wrote.markmiller said:you are correct, except that our cars with boost upgrades can see well over 300lb of cylinder pressure. these extremes love more octane as pinging causes much more damage under these conditions. and the article you quoted confirms this. better octane, less chance of pinging(detonation)
when we raise boost in an engine, the quality of fuel becomes a major issue very quickly.
Many WRX's that have been built(internally) for years will have the cat removed, run race gas, and make 70hp more.
this has been proven many times over.
ask any high horsepower b18c honda guy with a big turbo what happens when he increases octane.
I hope this helps.