1998 Ford Windstar Stalls

Current Problem: The van starts perfectly fine, and for the first 5 - 7 miles before the engines is warmed up it runs well. Then all of a sudden the engine loses power, starts missing, and runs unsteady for a little, then dies. But then I switch off the ignition, start again, and it runs well for about 2-3 miles and the same thing happens again. When I keep doing the Off and On procedure the driving spans get shorter. After parking for awhile letting the engine cool off I get a longer driving span again.

Recent repairs:The van also had starting problems a while ago and I had a repair shop put on a scanner which showed two oxygen sensors not working, so we changed those. That lasted for about a day and the van wouldn't start again after which we changed Fuel pump. That solved the starting problem. But the Current problem was still not solved, though the engine light didn't come on again and the scanner is reading no codes. I now removed the Catalytic Converters, Changed Fuel filter, and the problem remains the same. What else could the problem be?