Time to tackle it again...
This has been an ongoing issue since I have bought the car. I've kept track of all mileage and the average I get around town+freeway is 15-16mpg. On long trips between states, I get 19-21mpg.
Bought car 2006 @ 66k, I'm now at 107k

Spark plugs are OE H9DC0
New wires, rotor, cap, ovp, (used) coil
New o2 sensor, Duty cycle is closed loop 50%
New injectors + seals
No vacuum leaks of any kind all hoses replaced
Rebuilt Fuel distributor + EHA
All filters and fluids
No fuel smells or any sort of fluid loss.
Head has been rebuilt.

About the ONLY item I have not replaced (although checked volts) is the airflow potentiometer....Voltage came out to spec.
I guess also the idle control valve?

I plan to flow test the fuel system to make sure that comes to spec, but I can't imagine its bad since I've replaced everything including the distrib!

Any other ideas or suggestions?

I KNOW I should be doing better than this. I would be much more content if I was getting ~20mpg average and I believe I should be.

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2016 Monsoon Gray Audi Allroad - 21k
2008 Black Mercedes E350 4Matic Sport - 131k
2014 Jeep Wranger Unlimited Sahara - 62k
2003 Gray Mercedes ML350 - 122k