[SSDiv6]

All racing fuels contain Triethylamine.
They will kill the leather and even the Viton cups that usually come in the carb kits sold at auto parts stores.

I recommend the use of cups sold by companies such as Quadarjet Power, Quadrajet Parts, and others. They sell cups that are resistant to the new generation of fuels and are made from either Butyl, EPDM, Neoprene, or Hypalon rubber.