Well I am not sure on his hydroloc theory I think he is just lucky. There can be at least one exhaust valve open when the engine is off. The sea foam "liquid" could potentially enter the cylinder through this open valve, which means some sea foam could remain under the compression stroke. This would be bad I would think.
I tried a couple weeks ago to use the Sea Foam spray, not the liquid. The Sea foam spray is intended to be used for many things but specially the air intake. The can comes with about a 1 foot red spray tube.
Thinking I had a sticky exhaust valve I sprayed up inside the "Y" pipe on my 545i. I took a 1/8 ( maybe smaller) drill bit and drilled a hole in the top of the LH pipe as I have a P0492 only( about 2 inches past the "Y"). The hole was just big enough to put about 6 inches of the red spray tube into. I then started the car when cold. In this cold temp the pump runs a good 60 to 90 seconds. While the SAS pump was running I sprayed for about 4 seconds into the pipe. I then quickly shut the car off and let sit overnight. The next day I was ready to go. When I started the car indeed a cloud of white smoke came out. I drove for a couple blocks and the smoke dissipated. This was not carbon though this is sea foam as it is an oil - smokes when hot duh. (Video stated smoke was from carbon).
At least the smoke tells me I have some open passage but not enough to allow the volume of air from the SAS.
I have now done this a total of 3 times with no luck. No other problems have occurred as a result of doing.
To the point of the video I am indeed trying to see if a safe cleaner will dissolve the carbon over time. I don't think it will. I have heard and read that the carbon is very hard and must be removed while the head is off.
I have decided to give up on this SES light and P0492 code. I have 11 months to go for the next emissions test. Its only for initial start and causes zero drive-ability problems. To think anyone would spend 6 to 10K ( 1 or 2 heads) does not make sense. When I am ready to drop that kind of coin, it will be a down payment on my next one.