Well your problem has sat here ,unanswererd for almost a week.I'll take a
stab at it. I am usually wrong,but the good part is that it will surely
bring out the best in listees when they tell me I am
wrong ,here,below.Maybe then they will take your issue up. I hope then you
will have the help you need.Have a safe passage over those mountians.Wish I
was there.

I think your problem may be an exhaust leak.Basically, you are good to
proceed.  I currently have an exhaust leak ,and your symptoms are similar.I
have had exhaust leaks before without symptoms of almost any kind.Indeed,I
had a leaky exhaust pipe at the #3 cylinder flange. No symptom except a tad
louder exhaust,and a failed safety inspection.The po had wired a welches
grape juice can to the flange for the fix.Like I say,no symptoms.

My current exhaust hole,leak,is of the pin hole variety.It is after all 4
headers come together ,and next to the oxygen  sensor(1.9).It wont idle .It
stalls,backfires.has real bad drivability(whats new).I took it to a shop to
have the exhaust checked.I had to rev the engine to keep it running for the
mechanic to check it out. I sat in the van way up on the lift.A small leak
at the o2 senser was the villian(still is). I also suspect this  as  your
problem as you say it is getting worse.The pin hole gets bigger and the
symptoms get worse.

I would check your exhaust carefully.You got guts to be traveling is such a
hybrid ,way out there .Once again,wish I was there.
Roger