Wow, I wish you had been buying all of that stuff from me I could have my
kid's college paid for by now :)  (Sorry now on to the serious stuff)

You have replaced most of the things that could cause the problem, however
there are still a few things to test.  Try pulling your injectors and testing
them per Bentley to be sure they are not leaking, and also spraying in a nice
pattern.  Have your fuel pressure tested with a gauge.  Try unplugging your
Oxygen sensor and running the van that way.  If this solves the problem then
you could have had a bad AFM which killed your new Oxygen sensor and then the
oxygen sensor is causing the problem now that you have changed the AFM.
Try to take your van to a shop and get them to check your CO (mixture).  See
if adjusting it (via screw in AFM) would help your situation.
These are just a few suggestions.  Please let us know what you find out.

Thanks,
Ken Wilford
John 3:16
www.vanagain.com
Phone: (856)-765-1583
Fax: (856)-327-2242