This is a topic that has been covered many times here BTW. I still run the TD04 with stage 2 upgrades. Average hi-way mileage is 26 for me, but have achieved 29 when really trying. Combined driving, I average about 22. On track (road course lapping) I have gotten as low as 8.5.
Point is, your driving style and habits will dictate your MPG up to what the car is capable of. If you're a stop light racer, expect your city MPG to drop into the teens. It's all about the weight of your right foot, and how much you love the boost !!