Can someone confirm my suspiciions?

This IP has a fairly large vacuum line running from the back of the pump to the intake manifold. I believe this is the altitude compensator for this pump.

If I connect a vacuum to the back of the pump where this line connects it will not hold vacuum.
Does this mean the IP diaphragm is bad and needs replacing?

This car at 3200 fet asl smokes mightly but at sea level does not.

It appears to be a straightforward procedure to replace this diaphragm but I would like to confim this before I pull the pump and tear into the back of it.

Thanks

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'99 S420 - Mommies
'72 280SE 4.5 - looking to breathe life into it
'84 300SD Grey - Sold
'85 300SD Silver - Sold
'78 Ski Nautique