For my 1968 Cub Cadets and other equipment, each gas can gets MMO and Start Tron gas treatment. NEVER had a problem. One Cub is set up for snow removal and the other is for grass duty. Snow Cub sits for 8 months and starts right up.
My 90 Suburban ( 350 ) was running rough and my mechanic suggested Seafoam before he gave it another tune up ( it was about 30K since the last tune up.
Talk about cloud bank from the smoke
Ran great after that, pushed off the tune up for many more miles.