Ditto on the exact same issues with my 2016 NH workmaster 33. Won't go above 1800 RPM. It acts like it goes through the burn cycle but no smell and no change. Took filter out and cleaned it. Looked like another ceramic filter at the back of the housing. Couldn't figure out how to remove that one for cleaning. Removed what I could soaked in bucket and degreaser. Got a bunch of black sludge to run out when cleaned with water pressure.
No change. Thinking of buying the Chinese code reader but want to see if anyone has used it with success.
Was quoted by local dealer to clean filter for $1300. Robbery level costs.