Pilot screw plug #32 is certainly not needed. It is actually a metal anti tamper plug that we all remove anyway. The other plug you refer to is #21 and I do not have a definitive answer. I worked on a Bing or a westerbeke carb a few months ago and it had very similar rubber plug and it was needed for sure based on some research. it was solid though and this one looks to possibly have a hollow middle. Have you figured out anything more ??
P.S. can everyone guys see these pictures the way i am doing it ??