1992 300CE Fuel Issues

[thebighawk]

This is my last shot, kind readers. I bought, what I thought, was a nice example of a 1992 300CE. After a ton of work on this puppy, I still have bad fuel mileage.
Whats been changed trying to address this is, not in consecutive order: EHR valve, fuel distributor, air intake breather hose, to alleviate gas smell, A/C Acc temp sensor, water temp sensor, air temp sensor, dist cap, rotor, reference sensor, aux cooling fan relay, crank sensor, O2 sensor. Quite a list and still only getting combined mileage of 16/17. On a run on alligator alley at 80/85mph, I got 23mpg. Plug wires looked good, per my mechanic and the "specialty" benz guy I hadlook at car.
Is this the best I'm going to get, and quit griping, or is there something everyone has missed?
Also installed, ABS pump, timing chain, serpentine belt, alternator, compressor, dryer. More $$$$ than I paid for it into this so far.
Any one have a magic wand for this, or am I stuck. My 86 300e and 95 E320 both did much better.
Thanks in advance.
Embarrased