Stiff rubber

Based on the title of this thread I was expecting it to be about Viagra alternatives

 

...that was my thought as well, can't imagine GM requiring a one-off firewall plug...

 

you mean after all these years you don't have an organised shelf or wall with boxes and part bins and drawers full of all the bits and pieces and plugs, gromets, light bulbs, fuses, ash tray, lighters, switches, connectors , and any little Buick part for body, interior, ?????