A friend and I sat and discussed this over a couple beers last night. If I am right about what their theory is then normal decarbonization won't work. The problem is not in the combustion chamber but in the passages through the head that takes air injection into the exhaust.

We need a response here from someone that has viewed these passages. I remember there was a problem with an oil cap loosening and allowing oil to pass through the air injection castings and smoke like H*ll. I have read it but not seen it. My first concept on how to clean this would probably involve a reaming attempt after pouring something through the passages like x66p.

I will check the archives at a couple other sites, I know I have read the "fix" for this type of problem.

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Steve Brotherton
Continental Imports
Gainesville FL
Bosch Master, ASE Master, L1
33 years MB technician