From the Auto Forum:
Garbych: Recently, in the exhaust system, an interesting sound appeared. Pressing the gas pedal when switching the transmission, appears, sorry for the expression, a light, virtually unheard "popping". Once there was a flat bull, and now this is the sound. Is it gasoline or something else?

ponchik777: the shutdown
Wow, how ugly you are 😉
ponchik777: ughu... let her loose well... awos and the sounds will disappear
But yes, it really is crazy...)))
ponchik777: what about the smell of exhaust? What special shades may have appeared?
Garbych: As you guessed... it really started to smell differently in the room...
ponchik777: Are you sure that the sound from the engine?