Okay. Since there is way too much going on right now, let's make a flow chart to help cover what was done and not. We'll start at where it starts.
1. Fuel is pressurized by the pump then goes through the filter to the regulator.
2. Fuel is regulated to the injectors.
3. Fuel enters the combustion chamber. Plugs, compression, exhaust.
4. Exhaust Gasses leave the chamber and enter the manifold and flow to the cat. (Checked) then run out and exit the tail pipe.
5. Things attached to the motor, fan, alt., evap system.
Failing injector leaking excess fuel into the chamber, possible.
Don't think a failing fuel pressure regulator would cause bad fuel economy, but measure pressure while running.
No exhaust restriction
Compression is good.
Fan clutch check out iirc.
Plugged evap? I don't know.
What else is on that line that could cause issues?
Edit:I know I missed a lot.