Originally posted by SonOfABoss:
Take the new 02 sensor back out and check it, you may have messed something up... Switch to 89 or 87 oct gas, that will improve gas mileage also... I noticed a 2 mpg gain just from switching from 93 oct to 89 oct... Replace the plugs,wires, and fuel filter... If that still doesn't help, there's one more thing you can replace.......the car 
Sure you ain't got that backwards? I get GREAT gas milage when I run premium (93 octain) about 22.5 mpg compaired to reg gas at ~19mpg all in town!
