2.4l turbo Legacy motor

The 2.4l turbo motor in the Legacy is the same motor as in the WRX, but has something like 15 hp less, but 5 ft. lb more torque. I'm betting that most of this is due to a more restrictive exhaust, but also because of using 87 octane gasoline. However, I heard a rumor from a Subaru mechanic:

He claims that this motor will actually make better power on premium, and that it is "mapped" to benefit over a wider range of fuel octanes than the average motor today. I'm not sure if that is true. I remember that 20 years ago, the Toyota V-6 in the Camry made about 20 hp less than the same motor in the Lexus, and the only difference was that they had differently-mapped ECU's, which required the Lexus to use premium. Many people would switch their Camry ECU's for a Lexus ECU, and just use premium.

So, can anybody confirm this rumor, or disprove it? The possibility is there, and I believe that since the manual says it runs on regular, that's all they have to use when going through the EPA tests. Pay an extra $.40/gallon and gain power? Sounds interesting...