Oh forgot most important thing about this:

With new master cylinder installed and all hooked hydraulically up pretty much no power brake assist at all! But when I drove it brakes worn but ok.

Could hardly handle braking in parking lot. So left at shop.

So there is more wrong than engine not shutting off.

I have no power brakes now and u can't drive care without assist I learned.

Doesn't this point more to the power assist unit having a leak. Maybe a seal was ready do go bad and went bad when new master cylinder was put on?

O'ring? brittle, etc?

Unless I'm over looking something I sort of think there is major vacuum leak inside vacuum module as mechanic says and I agree too.

I have FSM and I'm going to look for Brown hose. Thanks.

Steve

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1982 300SD