How much gain could there be from a more aggressive tune for premium fuel?

So, the LLT makes 304hp on 87 octane.

Assuming somebody cracks the PCM and figures out how to tune it (or have the CTS guys already accomplished this?), I wonder how much more power is sitting on the table from a simple change to 91 or even 93 octane and a corresponding advance to the timing parameters.

Anybody have any idea?

very little if any.

It is very efficient as it is......

adding octane resist detonation, witch is caus by your more aggressive timing, that is not needed in an efficient engine to make more power.