FYI, it might not be the diaphragm that's bad.

I had my IP rebuilt a few months ago at the urging of the local indy. It turns out that my diaphragm was in decent shape, but the bearings and seals on the poppet cam were worn. Either will cause a vacuum leak and related smoking issues.

I don't know how you'd isolate that with the IP still on the car, but perhaps someone else does.

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1974 240D "Boldie" 170K.- New timing chain/freshly rebuilt IP/replaced valve seals/injectors/upgraded stereo/new Bilsteins with Yokohamas/fresh paint and rocker panels plus lots of welds.