I had the test run on my Benz W140 (223K miles) last week before leaving on a 2K mile trip. As I have stated before CEl code PO410 only shows up at cold start once the engine goes thru self check. If I race the engine slightly during the check I get no CEl. The Benz Tech told me I have a slight carbon build up on the right side(passenger side) of the engine. The drivers side is open with no problem or detectable build up. Is there anything I can run through the ports which will semi clean to clear it enough to prevent the CEL? If there is can it be done by running it through the pump vaccuum or is there another place? Thanks for the reply I am trying to do this without having to pull off the top of the engine. All the best, MBD