Without knowing what kind of dyno you used its hard to say if your car is running at full power. I don't know a ton about dynos, but I do know Mustang dynos run on the low side so that could explain your low numbers. Depending on dynos from what I have seen stock cars are from mid 280's to 300 (freaks). Although as previously stated, Mustang dynos run lower. Find out what kind of dyno you ran on.