Looking great man, good to see you doing what matters most first, making the car look clean and have the basics in good shape!
I also agree 230 is really below standard for this vehicle. Generally the gauge will read empty at 10gallons, luckily for us that makes it easy to calculate gas mileage! So you would be getting 23MPG. It has been a while since I had my stock de in, but you should be looking at 275-300 if I am not too far off. Enjoy the car, and keep doing what you are doing!
Good luck, and look around the forum, lots of information, don't forget to search, it will take a little bit to get good at it but it will pay off in the end!
Dudeman