Those numbers look right to me, you used a mustang dyno which will read around 12% lower than a dynojet. Multiply your numbers by 1.12 to get close to what you would have made on a dynojet. Mustang dyno's read lower than other dynos do. So your best peak was 297.92 which is good.

Heat and humidity has a big effect on numbers too. Did you let your car cool down an hour or more before you ran on the dyno?