Ah gotcha. So you may not be aware, but the terraclean carbon clean service is also a hydrogen clean - different to their other fuel cleaning system (which will have no effect on carbon in the intake manifold). I'd not heard of pro - clean, but this seems to be a cleaner for disassembled parts according to their website. I can't comment on how it works (or not) as I've never tried it. However, it's still going to involve most of the labour cost of a proper manual clean: I.e. Taking the manifold off and putting it back on once clean. The system I tested was Enginecarbonclean, a company that was doing the rounds on the forums and seemed to be the most popular hydrogen clean provider.
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