But the higher octane will allow the PCM to have to retard the timing less under high load to keep the knock sensor quiet.
More advanced timing with higher octane fuel should get you more power because the piston starts pushing earlier and the power is released in a more controlled/usable manner without the earlier and higher peak pressure (of lower octane fuel) setting off the knock sensor.
It's the area under the pressure-time curve which creates the total power during a single power stroke. More area (total power) results from longer, more even pressure duration (from higher octane) than a shorter duration, higher-peak pressure curve (because it's that quicker-rising and higher peak that the knock sensor interprets as knock, which, again, retards the timing in future cycles, delaying the start of that nice, more even pressure curve).
The Special and non-Special engines are the same stroke, bore, and compression ratio, so pre-ignition should not enter into the discussion (of which grade of fuel to use). Pre-ignition is the fuel detonating (purely from pressure and temperature) before it sees the spark - hence the term "pre-iginition". Timing changes due to closing the loop on the knock sensors can do nothing for pre-ignition. A Special and a non-Special engine are no different as far as tendencies to pre-ignite with any particular grade of fuel.
'98 LXi - Later Concorde gages (black w/ chrome rings)/'99 LX - LHS gages (white) - HIR bulbs