Drastic loss of gas mileage in 1993 Dodge Dakota?

I recently posed this question but nee to inquire again. I have a 1993 Dodge Dakota with a 3.9 Magnum V-6 engine and the gas mileage dropped almost over night from 17-18 m.p.g. to less than 10 m.p.g.

I am not getting any warning lights. I have replace the o2 sensor, EGR valve, plugs, wires, cap, rotor, gas cap, gas and oil filters and an oil change, IAC valve, any valve that connects to the carb/emissions system, thermostat and antifreeze, and replaced a couple of vacuum lines. There is no improvement in the gas mileage.

The timing is correct, the compression is good, there is no fuel leakage, and no vacuum leaks. The vacuum canister appears to be functioning properly, but not something that I think needs changing because I don't believe it would double my gas mileage. What am I missing here or what could be wrong that is failing to provide me with any warning codes?