"Race Gas " is fairly generic and it would help to be a bit more specific. But in general, you certainly need to adjust the tune of your motor to take advantage of the benefits that most race gases will provide. Each particular race gas is different, and so what those benefits are (as well as down sides) depends.
But generally if your motor is knock limited which limits your ignition advance, then race fuel will allow you to adjust your advance closer to your engines best timing for power.
Without making any tune adjustments, you will likely not see any improvement or see a reduced level of performance. Many high octane racing fuels achieve this higher octane by using longer hydrocarbon chains which tend to slow the combustion process, allowing it to resist detonation. But if you don't push things harder with such a fuel, you can see lower performance.
You may also find you need to increase your fuel mixture or even lean it out a bit to optimize combustion. Sometimes you need to change your plug gap, or even a heat range (some race fuels burn colder)
If you ever spend time at the track on a test and tune day, you may notice the cars that go down the track. Then hit the pits, work on the car for a while, then go back out. Often times the are pulling plugs between runs and reading them to see how they may want to change things up. We have the benefit with the quarterhorse chip, to datalog our runs and see what's going on, then change things back in the pits.
