What is the forums experience with decarbonization of the turbo 4’s intake valves. My dealer is recommending it at 30K miles. Seems to me like a revenue generator for the dealer.

 

I wouldn't do it, and the manual specifically states do not use additives. Having said that I generally use Top Tier gas (google top tier) which is of some benefit. I will also tell you that when I owned a Porsche that suggested only using products like Techron or Seafoam about 500 miles prior to changing the oil. Research had indicated that a great deal of the additive remained in the crankcase and the potential for harm was reasonably high depending on driving habits. Something like Seafoam is likely all the dealer is doing and likely fleecing you out of $150.

Honda also has looked at the issue through engine design. See