First of all, I like what you did to your car. The Si rims flow with the car IMO. Did your original engine krap out on you or just an upgrade for horsepower? If a front license plate isn't required in your state, then I would take it off. Also what about the civic hybrid lip, it looks nice and would probably help in aerodynamics which is what you need since you are driving highway miles. Also a freer flowing exhaust might help out. What's your current fuel economy?
Hybrid lip:
Can anybody here confirm that it would help in aero?