I took the rim&tire to a very reputable tire specialist I have known for many years today. He advised me to get a new tire, which I had to order as it was not available in store. He showed me two tires which he did a week ago - installed mushroom plugs - both started to leak after a day or two. His experience is that plugging a hypersport tire like the Rosso Corsa II is a gamble. These tires have very soft walls as well as tread areas. New tire will arrive Friday.
Mushroom plugs are garbage, of course they started leaking. You're taking advice from a guy who's livelihood is selling tires. Making plugs out to be unreliable makes him more money.
Dude played you like a piano.