95 3.8 backfiring

Van ran fine this morning, went to start it this evening to take grandkids home. Engine fires up right away, climbs to about 1400RPM, then quits like you shut off the key, followed by a backfire from the intake. Numerous attempts to restart the same. Sometimes by feathering the throttle you can get it to run, but very rough, backfiring, and it seems like the rev limiter kicks in around 3500 to 4000 rpm, it will not go higher. Release the throttle and it quits.
Fuel pressure just within specs at 41 PSI. A timing light put on all 6 cylinders shows spark. PCM grounds cleaned. No trouble codes present.
I did notice the inject pulse width sits at 40 to 50 ms with engine shut off, key on, shouldn't it be zero? Changed out the PCM with another used one thought to be good, no change. TPS doesn't seem to have any flat spots in the data, smooth linear change from idle to WOT. MAF data does change during the engine's brief run.
Anty suggestions? Gotta get it running soon, good wife clamouring for something new and shiny in the driveway, hard to fend off that suggestion with a van that won't run.Thanks Jeff

The maf data should change under driving conditions, they were troublesome back then and until obd11 they had no default setting, if they failed. No codes I assume?

No, no codes thrown. MAF does go from zero at start to about 5 before the engine stops, this is under a second. I did unplug the MAF, forcing it into limp in mode; MIL came on but no change to driveablity issue
Jeff

Well, good news, can keep the circling car salesmen at bay, van up and running. Problem was with the EGR circuit; where the EGR outlet pipe fastens into the plastic intake manifold with a large plastic nut. Apparently the tangs were missing, and looks like had been wearing for a while as things were smooth. Naturally this part not longer obtainable, so a generous dollop of JB weld was used to stick things back together.