I don't see how pouring anything down the spark plug hole will help clean the back of the intake valves, which is the real problem.
I would generally doubt the effectiveness any intake valve cleaning that doesn't involve removing the intake manifold.
I would worry how much of whatever you are pouring into your engine will seep down into your oil. I would change your oil immediately after this treatment.
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2009 BMW 135i 6MT Sport, AFE intake, Cobb AP, Apex 18x8.5+9.5, 255/275 PSS
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