> Basically it would lose power like it was out of gas and die somewhere on
> the highway. We would either wait awhile and it would come back or it won't
> start up again at all,  .....

> The last breakdown was in June 2020, .... Currently it starts nicely,
> and idles well for a few minutes at about 900RPM, then idles rough, no
> response on throttle, with high gasoline vapor in exhaust and loud
> backfire. Attempting to drive stalls the vehicle.

Caveat: I didn't read your entire post.

If a tach is present, a tach needle dropping when engine issue happens
might indicate that the issue is electrical in nature.

The inner lead on green shielded O2 cable on vehicle harness may be
shorting to cable shield.

A failed and clogged cat might cause what you see.

If vacuum hose to fuel pressure regulator is leak free, while it's
attached to FPR, if you can blow (gently) air into it, the diaphragm
in FPR is broken.

Try to recreate the issue(s). Note if they *only* happen once the
engine is warmed up.

A PDF of the Digijet pro training manual can still be found online AFAIK.

I doubt Vanagon syndrome is the issue but to me, the VW TSB on VS
indicates that VS can also happen in Digijet.

Neil.

-- 
Neil n

VE7TBN

1988 Westy 50º ABA swap: https://tinyurl.com/yap5hpwt

1981 Westy 15º ABA swap: https://tinyurl.com/y9n4xob8

VAG Gas Engine Swap Group <http://tinyurl.com/khalbay>