One more snake oil product among the hundreds (or maybe thousands) already out there. And don't get all carried away because Speed Channel endorses it. They get paid to advertise and endorse products. Kind of like American Iron when they publish a "test" of products that just happen to have full page ads in the same mag.
Gotta go, heading out to the garage to "soak" my metal.
Jerry
Oh, if you want to clean carbon deposits off your valves while cleaning your injectors, try one of the many gasolines sold here in the USA. They all contain detergents by law which will perform those tasks, and some contain more than the law requires as a selling point for the Premium fuel. Walk into a Shell station and you will likely find a little display of a dirty valve next to a clean valve, just like the picture on the zMax site.