Race gas definitely means more power, but it is expensive to run. When I go out to the dunes, I run through roughly 10gallons a day, which comes out to $150 daily to run 110. If you don't ride much, or your wallet is fat, then go for it.
You should be fine with the cylinders you have, if you want more power send them out to one of the sponsors of BHQ for a dune/trail port. You said you ordered new pistons, you should read the number on the top of the old pistons to see what size they were, that should have told you the bore size. If they were the 795s for a 4mil and it truly was standard bore, they should have read as 795M06400. The last 4 denote the bore size, 64.00mm is standard. If you are putting in new pistons, I'd recommend just getting a bore done when you send the cylinders out for porting. This way you can get the pistons matched for your setup. Go to like a 64.50.
When I bought my trail bike it was already at 65.5. this means it had a bore done several times, which was expected from a 30+chest old bike. You should make sure of your bore size by checking the old pistons out, as people do this usually when they purchase the bike and most banshees are now old enough to buy alcohol.