Ive had to establish before that there is a vacuum leak by simply spraying carb cleaner or wd-40 down the throat of the carb or intake before the mass air flow sensor. if the engine runs well when spraying, you have a big time lean condition. Then its a matter of locating the hose and/or assembly that's leaking, such as an intake or the air plenum. No sensor is going to cause this much of a problem, even if the mass airflow is hosed.
This is what i've nicknamed a "global" air leak, meaning that all cylinders are affected, not just one like some of the GM v-8's are famous for doing. Something that massive and you should be able to hear it.
Man i wish i was there, i know i could find it!!!!!!
A cracked PCV hose will do it, i've seen it happen, from a slight miss, to no idle whatsoever.
The brake booster and PCV valve are easy to trouble shoot, just simply cap them off at the source and see if the problem goes away, no driving needed.
Just a few months ago i repaired an all original 1967 Oldsmobile 442 with a no idle condition. The guy complained of non existent idle, hard pedal effort on the brakes, hard starting. I found that the brake booster was leaking and the original carburetor was cracked at the base plate. Car runs great now, and it will scare the hell out of you 
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