Put a compression tester on it and find out what it's cranking. E85 is not what you need to increase pump premium's octane. To effectively increase your octane, try running some % of 100 octane unleaded or add 110 octane leaded to your tank. You will have to rejet no matter what you do when you start blending your fuel, so be consistent with the mixture once you get a ratio that works. You may want to get a knock sensor to detect detonation and a wideband with data logger. FAST has a nice wideband unit.

I only drive my car for fun and rarely burn more than a tankful a month, so I intentionally opted for high compression (12.8 to 1 @ 225psi cranking). I've always liked how it runs with it, and I don't really care about the cost difference to run high compression because of the performance trade off. I don't drive the car that much. Also, I know you can't get 100 octane unleaded everywhere, so I had a larger tank made to extend my cruising range.

I do have to pay about 1/2 again more for each gallon of the fuel to meet the octane requirements. I was going to mix 110 octane unleaded, but that's illegal in California now. Fortunately, my motor likes the 100 octane unleaded at about $6.50 a gallon.....and rising, but I knew this going in. Sounds like you didn't know your compression is too high for normal pump gas.