The Racetronix Walbro 340M that i have here in front of me along side the GSS344 both have the big inlet FS111 fuel sock on them and the Walbro 340 i have in the tank right now has the same fuel sock.
I don't know what the differance is or supposed to be, but i do know what i'm using for the fuel sock and it fits perfect for all 3 pumps i have, FS111.