and also check the timing also. thats another thing that could effect it that i forgot about.

 

I'm original owner of 97 HX. I average around 38 mpg on combined mileage(city and highway). When gas was hovering around 4.50 dollars, I drove the car like a granny. I would get around 43 mpg. The only time I got horrible mileage, the throttle body was dirty.