Nissan Repair: 1989 D21 Nissan Hardbody Z24i issues in wet weather, nissan hardbody, vacuum system

Question

1989 D21 Nissan Hardbo Hi. Until recently my 1989 D21 Nissan Hardbody Z24i has been running fine - and it still does in warm, dry weather. However, when it is wet it does not run well, choking, stammering and stalling under throttle. Seems like fuel delivery, or spark plug misfire - can hear a engine 'backfiring'. Also, noticed that there is a part attached to the vacuum system that is totally corroded (photo attached). Not sure if this may be the culprit or not. Would like to avoid randomly replacing parts as I plan to sell the vehicle.

Answer
Ben,

I would replace the cap, rotor, and plug wires.  The indication is when you say it does it in the rain.  Tidy up the rusty bits but they should not be the cause of the problem.  It is most usually the things I mentioned for the cap, rotor, and wires.  I would go with new plugs while I was at it.  But, you do not need to unless you want to.  Cap, rotor and wires is a must.