I hear ya, This build is going to cost big money ( for me anyway). i would not risk the distrucion of my motor just to save a few bucks at the pump.
I would use an additive as a precaution as well. I don't plan on racing a 3700+ LBS. car. I just want her to have some giddy up. Ok, it would be awesome to have a 500hp sleeper. I live here on earth and I know that won't happen with the 340. I'll settle for some more giddy up. I have a two car garage. And a relatively reasonable woman.