From my experience, the Seafoam doesn't clean nearly as well. It's not nearly as volatile, however, and so while B12 will probably pass through the intake mostly as a gas, the seafoam will resist evaporation and actually do something. But, again, from what I saw, that's not much. Soaking my intake in B12 cleaned it - I mean really got everything, with no scrubbing. Seafoam didn't seem to eat away at it much.
