In as much as I don't want to isolate it and instead fix it, I would be very thankful if some GOOD BODIES around could help me.
Vacuum Converter 84 is picked when keyed in and I got about 7.5"Hg Vacuum,
but when keyed out VC 84 drops out, of course, losing vacuum, thus, engine is not shutting off. Meantime, I just cut out Vacuum line to VC 84.
"What make VC 84 stay picked when I key out"?

No reason to keep the EGR functional, unless you're building a concours quality restoration and need 100% original for judging purposes. You'll be happier and so will your engine if you just remove it. There are kits available to remove it, or just cap the vacuum to make it inop.

You can remove a bunch of vacuum lines and make your engine bay a lot cleaner too (helps eliminate leaks as well)

Here you go

__________________
Current Stable

• 380SL (diesel)
• Corvette C5
• Manx
• Baja Bug
• F350 Powerstroke
• Auburn Boattail Speedster replica

HI mach4,
Thanks much for giving the suggestions/advice. I am thinking of retaining the
EGR function, helping the engine stay clean. I am also in contact with DeliveryValve, who also gave some better diagnostic advises. I am nearly concluding that VC 84 is defective, since, it doesn't hold the vacuum as soon as when keyed off, thus, loosing it and not shutting the engine off. Meantime, I will do more tests to confirm the defect.

Confirmimg that VC 84 is bad. Made modification by adding check valve to VC 84 vacuum supply line and it worked!!!
To all buddies, thanks much for the concern...