O-ring part number

["georad1" <georad@xxxx>]

Hello Group, I'm reinstalling the air plenum and mixture control
unit on #2196 and need the part # for the o-ring that goes on the
idle speed motor airpipe to the mixture control unit housing. I 
can't find it in the parts book.

Thanks
George R. Radomski
#2196
working on #4258