The ECU does not have any way to advance timing past the factory tables. Only retard timing based on knock history.

However the aftermarket tuners are able to add timing/trim fuel to gain power. Most of the aftermarket tuners for these cars are able to get 20~25hp just by tuning from 91 to 93.

So for sure it's down on power with 87 in it.

By the way... As for the ECU learning. The idea of watching knock count and tuning the timing tables through long/short term "trim", has been around for at LEAST 30 years.... as I know my '93 Mitstubishi Turbo Eclipse had this functionality. These things are WAY smarter then you think they are.

I don't know what you mean by "load up", but for sure the calibrators know that people will put varying degrees of fuel quality in these. The PCM will adjust to whatever you throw at it within reason.