Gumout multi-system tune-up Vs Marvell Mystery Oil (MMO)?

[sciconf]

@Mustangman

I let Seafoam be sucked into the intake, let it sit 30 min and then do the Italian Tune Up like it says in the instructions on the can.

How often you do it?
Should there be a concern of things getting damaged with the use of Seafoam? Amazon has such reviews though.