1992 Toyota Corolla uses too much fuel

There could be an exhaust leak near the O2 sensor.
The throttle body was serviced as well, I am assuming. Did you replace the throttle position sensor, (TPS)? It has to be calibrated to manufacturer specs with a multi-meter as well.
Other possibilities are;
A bad ECU
Vacuum leak
Check to first items on the list and get a Haynes manual if you don't have one.
Tracking down bugs after a complete overhaul can take some time and not always be what you would expect.
Take some time to make sure everything is calibrated and break it in correctly.
Remember, a motor uses more gas when it is brand new and gas mileage will improve as the engine breaks in and things will change with time.

Did you calibrate the TPS?

If there is an exhaust leak near the O2 sensor the ECU will think the engine is running lean and dump more gas in the motor.
The Cat could be really clogged or burnt out that the same type of thing will happen. Cats are also prone to rusting through and leaking.
Also, check the donut gasket neat the exhaust manifold/cat connection.