The previous owner was far more knowledgeable and experienced than me, he said he ran 91 octane though he did not drive/own the car much before he sold it. He said it should scream on 94, but realistically I understand that if the car doesn't need it, it won't run any different and it's just a waste of money. 94 octane just provides extra Knock resistance. This 340 has a roller cam aswell, though that shouldn't matter. I know my old 360 with Aluminum heads and Keith black pistons in the Volare had some 10.5:1 compression, though again no way to measure. Sometimes it would miss in the upper registers and the power would Dropoff momentarily, so I guess this what I should be looking for?