I was looking in to this, hence my reason for deciding to going with a catch can kit after being against the idea.
It seems that despite using proper oil, fuel additives etc that the build up still happens. I am thinking that a manual clean of the intake valves may be more effective unless someone can prove that "seafoam" works and has no detrimental effects.
I was just thinking that whilst the catch can stops the coking getting any worse, it won't actually improve the situation you currently have. Dread to think what mine may look like at 28k miles
With the misfires I have, I may need some new coilpacks, plus new spark plugs, and possibly new injector(s). I have a new CAI on the way, and now need to consider a catch can, plus a 'seafoam' clean & then an oil change ......
Somewhere in there I have to pay for living, holidays and petrol! What a firkin malarky. I've just about had enough of all this.