1991 190 E 2.3 - low on gas = hesitation

I have a great '91 190 E - just had a head gasket put in, 89K- beautiful
shape.

When the gas  gets to about 1/4 full, it starts hestitating after stopping-
then gets worse as it gets lower on gas until it stalls out at every stop.

I have had a certified Mercedes mechanic go through every possible cause,
including draning the gas tank and cleaning the screen- but no residue was
found.

I have had advice from another- drive low on gas with the gas cap off, use
some injector cleaner additive, adjust some part that determines gas
pressure at altitude (?) and make mix richer- to "don't drive with  1/4 tank
of gas!"

Next step is new gas distributor?

Advice?

Thanks....