I have noticed recently that my 97' SR5 has gotten less gas milage than about 3 months ago. Any suggestions that I should look out for? The muffler and O2 sensors are fine. I also put in a new airfilter.

Too low air pressure in your tires?
Cold weather?
500lbs of sand in the back?
Gained weight?
More city driving?
More drag racing?
Brakes dragging?

Tune up overdue?

How long has it been since you replaced your oxygen sensor? Most people never replace them but you should replace them at least every 50,000 miles.

Check for trouble codes. A bad sensor could also cause a rich condition.

A dirty air cleaner will cause increased fuel consumption.

Replaced O2 sensor 4k miles ago. Replaced air filter 2k miles ago. I think im going to get a tune up this weekend.