97 e350 MPG decrease

[Bkubiac]

When I bought the van a year ago getting 19 to 20 was not a problem but recently the mpg has been decreasing and is down to 12. The van is stock other than a 4 inch turbo back exhaust. It is a cali van.

Things ive done

Fuel bowl cleaned and rebuilt a few months ago
EBPS cleaned and new tube installed
New fuel filter and air filters
No fuel leaks anywhere
No brakes dragging
All wheel bearings were repacked within the last 15k miles

Im basicallly out of ideas and would love some input.

It runs and idles great. Smokes for maybe 5 seconds on a winter startup and thats it.

ive only put 40k miles on it since I purchased it

I cant help but to assume its engine related. Maybe injectors a sensor or two giving bad data etc.

Thanks for any and all help.