I'm pretty sure it is MA legal.
Even if it isnt, they won't have a way to test for it...
Be aware that you will need to reconfigure your motor to make it worthwhile.
Datsun L-series motors that were making 105kW on AvGas, went to 107kW by simply filling with Elf. With a rebuild and retune, they went 115kW on Elf.
With a rebuild and retune to suit 98 pump fuel, they made ~108kW.