BZZZT!
Nice try, but unfortunately, incorrect. The removal of lead from fuel revealed a need for different valve seat material, but that was a by-product that had never been accounted for, not the reason lead was added to fuel. And by "lead," I'm talking about the octane booster tetra-ethyl lead [hence, the nickname "ethyl" for high octane gas, vs. "regular" for the standard grade.]
And modern octane boosters don't work anywhere near as well as a shot of avgas 100LL ["Low Lead" here is a relative term: 100LL has much more TE-lead in it than any road-going version of gasoline ever had...] All of which is great for those of us w/ Guzzi's w/o a cat in the pipe.
Thank you for your correction.............