poor fuel milage

I just got my 04 grand prix in may of this year, it has a series III 3800 not s/c it has 83000 km (80,000 when i got her) and i am not impressed with my fuel milage. I have changed the filter and cleaned injectors,but only helped a little,need tips before i pull out the rest of my hair. I am also lookin for a throttle body spacer to no avail:banghead: ps love the car though

It would help to understand what mileage you are currently getting and what you are expecting to get for MPG with your '04.
I am getting 24 mpg in the city, 30 mpg on the highway with my '04 GT1.