1996 ford windstar sputters

1996 ford winstar 3.8l keeps sputtering and eventually dies once in a while.
i get an obd II code that the egr valve fault and oxygen sensor out of range so i changed evrything, the oxygen sensors code went out but the egr faul code is still on, not sure what to do now. also why does the OBD II test always say test incomplete when i check it on any ford, i have the snap on solus pro scanning machine.

Have the EGR ports been cleaned?......they can cause the "sputters".

The DPFE is also a common cause of EGR flow codes.

For the OBDII test incomplete, it takes a LONG time for that test to finish the downstream oxygen sensor test.
Whenever you reset the codes, the whole test must run from the begining before you get the completed indication.

how do you test the dpfe?

I have not done it, but if you search this forum under "DPFE" or "Test DPFE" you will see instructions from forum members who have, you will need a meter to check the voltages.