Well then keep driving you car thinking it doesnt ping.
If you want proof, go to a shop with a dyno let them make a pull with your car stand inside where the car is about 15-20ft away so the nois isnt right in your ears. Listen close.... that sound that sounds like metal bb's being dropped in a coffee can or garbage can is detonation. I've been in 5-6 sti's besides my own, stock and modded they all detonate. Its such a big problem subaru issued an ECU reflash to cure it, but yours must be the only one that doesn't ping