Guys, we discussed this multiple times. Although the compression ratio is obviously mechanically fixed (there are experimental engines that have variable compression ratio btw), there some kind of margin for adjusting the timing, and if you put in higher octane fuel, to a certain extent, you get some benefit. After a certain point, increasing the octane does not make a difference. We have seen data on the E46 CSL that suggests this.
I also remember seeing one of the British TV programs testing a bunch of off the shelf "octane booster" in a proper engine lab. If I can remember correctly, none of them increased output, and some actually decreased output. I don't remember which products they tested exactly though or what the test engine was.