Does 89 or 90 octane gas make a 1994 firebird run better?

Contrary to popular belief, the octane rating refers to how RESISTANT the gas is to combustion. The higher the rating, the more resistant it is to burning. The action of the piston compressing the fuel-air mixture heats up the fuel considerably (a diesel works this way, they have no spark plugs) The heat of the compression alone can ignite the fuel before the plug ever fires. The explosion hits the piston while its traveling towards top dead center, wasting energy. The plug can then fire, creating a second explosion which meets the first, creating spark knock. Spark knock can be cured by running higher octane fuels, so unless you're car is knockin', I would just save my money. Yes, the power will go up a little, but it probably won't be enough to justify the increased costs.