That sounds a lot like my problem last year on the 91 2WD, Silvan. Found some intermittent rotten wiring in the loom near the AFM. It took a lot of sleuthing and time to figure it out. 
Good luck

Bob

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> On Jul 16, 2021, at 00:27, OlRivrRat <OlRivrRat@comcast.net> wrote:
> 
>         Fuel Gauge reads correct & swapping in a diff’ DCV Reg, just for curiosity
> 
> made no diff’ as expected ~
> 
>        Current state of functionality of this Van is that it runs pretty well most of the time,
> 
> some of the time, ie, it can do significant periods of high speed hiway runs without issue
> 
> & then get coughy & chocky on slow down & then the next day do over 200Mi’s of Mountain
> 
> driving without even so much as a hiccough & then days with bad times & good times & then
> 
> a day of good City Drives only to then a day of Bad ~ When Bad it seems like “Limp Home”
> 
> in that On The Fly You can Clutch, turn Igni’Key Off/On, release clutch & all is back to good
> 
> for awhile ~
> 
>        1 oddity that is a bit of a head scratcher is that during 1 of it’s Bad Phases, If @ Idle
> 
> or @ some 10 to 20Ks RPMs it begins to go stumbly & for some reason You decide to reach
> 
> for the O2Snsr wire, when Your Hand/Fingers get to very close proximity of the connection
> 
> between the wire to the Sensor & the wire to the ECU the Eng will jump in RPM & start to
> 
> run smooth again ~ My WAG is some sort of Inducted Signal to the wire from My Electric
> 
> Personality but I’m not aware that I have Such ~ Have DVM’d the O2Snsr Wire & Its related
> 
> Ground wire & All Looks OK ~~~~  HELP  ~~~~~~
> 
> 
> 
>> On 7 Jul , 2021, at 4:29 PM, David Beierl <dbeierl@GMAIL.COM> wrote:
>> 
>> If the fuel gauge also reads low then it's undoubtedly the instrument panel
>> voltage regulator.
>> 
>> Yrs,
>> d
>> 
>>> On Wed, Jul 7, 2021 at 4:32 PM OlRivrRat <OlRivrRat@comcast.net> wrote:
>>> 
>>>               David
>>> 
>>>       Thanks for that,, Reminded Me of 1 symptom I had planned to mention
>>> 
>>> but had forgotten > Gauge Indicates Low, Rad Fan Comes On when needle is
>>> 
>>> @ about 1/4 from bottom & RadFan Switch is fairly new ~
>>> 
>>> 
>>> 
>>>> On 7 Jul , 2021, at 12:11 PM, David Beierl <dbeierl@GMAIL.COM> wrote:
>>>> 
>>>>> 
>>>>> Another Oddity > Coolant Level Warning Light Flashes Constantly with
>>> Key On
>>>>> 
>>>>> Even with Connector Jumped & Relay 43 Removed ~ Any ideas on that ~
>>>>> 
>>>> 
>>>> Either gauge input voltage out of spec or more likely leaky timing
>>>> capacitor inside the gauge.  10 uF 16V.
>>>> 
>>>> Yrs,
>>>> d
>>> 
>>>