Don't worry so much about what the actual number is. Your right in the range you should expect and the dyno is just a tool. Your looks to see how this new mod (E85 tune) will improve over what you have now. The true test will come at the track.
New Ride -- 2015 Z06 2LZ (stock) -- Journal
Old Ride -- 2012 Camaro 2LT/RS (647 RWHP & 726 RWTQ) -- Build Thread