1992 Ford econoline e150, revs high, stalls, surges at stops, starts right back up, drives fine, mechanics clueless, help!

I've owned this van for 2 1/2 years and its been to
mechanic for 2 years of that pretty much
monthly...rebuilt trans, new fuel system and
pumps, air and water systems basically replaced,
new radiator and the basics, major tune up and
such.  Now my mechanic are stumped...she stalls
on occasion when stopping, revs super high after
driving, has a strange dipping idle in park and has
bucked a few times in the last three months. They
have sworn the egr valve and tps are fine, clean
and functional.
I often feel a flutter at 35 mph, she never
overheats, but when she stalls, she sputters and
dips a few times before dying completely. Luckily,
she starts right back up no problem. Also feels like
she doesn't need gas pedal depressed when
coming out of a stop when she's revving high.

If anyone can help that would be joyous mostly
because I love this van and have invested in her as
much as she's worked hard for me in the last few
years. I don't want to give up, I know something
needs fixing. Thank you!