Todays progress --
Inspection provided no joy. All vac hose connections are soft and well seated. Flexing hoses with engine running made no difference in idle.
Without removing fuel rails, I could only check tightness on three of the eight intake maniforld bolts/nuts.
I used this time to replace the S/C nose and get rid of the damn rattle. Fixed.
I visited the local garage with all of my info and codes. They put on a vac guage and said it was steady, thus no vac leak. I am not sure that is a meaningfull test, but their position is that I must go to Isuzu for a deeper diagnostic. No charge for an hour's work, but problem not solved.
I called and ordered intake gaskets. Merlin at St. Charles, says a new replacement part number is on hold to fill many back orders. 27 are in some warehouse and I had to give the VIN number to get expedited access to the parts. If I am lucky, it will take a week. He mentioned this engine is in the Honda Accura and many other models. All are/will have intake gasket problems and the new gasket part number is aimed a solving a wide problem. So much for Japan quality.
When I get the gaskets in hand I will visit the Isuzu dealer 2 hours away and camp out until fixed. Maybe they can fix the 1441 code at the same time.
Thanks for you help. Roy