At the Fall outing in Darien, I met a young man who was asking about the Boost Control Deceleration Device which is mounted on the bottom of the throttle control. It was used on some of the later 280Zs and the 280ZX.
The BCDD is no longer available anywhere as a part, and it would be impossible to restore. Its sole function is to reduce emissions on the over-run when decelerating. Working properly, it adds nothing to the cause, but when it fails it causes all kinds of problems.
After checking and replacing many other components and sensors, I was tipped off that the BCDD could be the source of my problems with bad hot starting and some slightly rough running. The device itself was also rattling a bit from loose internal parts.
The man who saved the day was "Oliver" who operates zspecialties.com. He will take your old throttle control from which you have removed the BCDD and weld the closure shut. No doubt there are plenty of other shops who could do the same job locally. Just repace the throttle and clamp off the vacuum pipes that were connected to the BCDD and you are good to go.
My 280ZX has run as smooth a silk since I ridded the car of that BCDD.

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1980 280ZX 2+2
2003 350z Touring
2005 350Z Touring - Silverstone Gray
CT plate PHILSZ