Orange light comes on...Help

[Vytautas Reipa <vytas@erols.com>]

Whenever my 86 5kcst(103k miles) hits 3k rpm under full-throttle
acceleration, the orange light on the dashboard comes on. This light,
according to my owners manual means that the octane rating for the fuel is
too low or there is a problem with the ignition system. The ignition works
fine on my car and I use Sunoco 94 gasoline. The light disappears when the
rpm drops. I have tried adjusting the ignition timing but the car then idles
roughly or does not start at all. Is it normal for the light to come on
during hard acceleration?