1995 Ford Aerostar van, AW hi, 4.0, 140,000 miles, white smoke with no smell under hard acceleration

1995 Ford Aerostar van, AWD, 4.0, 140,000 miles.
On a recent trip leaving Vegas pulling a pretty good load with the outside temperature 110 and with the AC and cruise on while pulling a pretty good grade, the van started dropping speed after the downshift and emitting a lot of white smoke with no smell. No missing or stumbling or cutting out and the engine temperature was normal. After topping the grade the smoking stopped and the van ran normally. Did it again 600 miles later under the same conditions and then back to normal. No starting problems, no shifting issues and coolant, oil and tranny fluid OK.
I had just refueled for the first time on the trip prior to the first time this occurred and to my surprise on my next refueling the mileage had jumped from 14 to 19 and subsequent refuels were 18 and 19. This van had always been right around 15 since I’ve owned it.
I’m obviously all in on the mileage jump but concerned about the smoke issue.
The van has vapor locked on me on a few times when the outside temperature is over 100 as the engine compartment is so crowded and gets very hot.
Other than that no issues, just curious about the smoke issue. Where there’s smoke there’s fire they say and it’s gotta be coming from somewhere.