Here's the writeup from Sea-Foam.
http://www.seafoamsales.com/motorTuneUpTechGas.htm

I've always been wary of the PCV method.
Introducing any fluid into the intake manifold is a little too risky IMO. :noes:

I've used Berryman's C-12 Chemtool to great effect with all the cars I've owned. With the DC4, I add two-thirds of a can to the petrol tank just before a complete fill-up. Later, right before I change the oil, I follow their instructions for use a crankcase detergent. With C-12, it is imperative that you change the oil immediately after a crankcase treatment.