So after posting a message about my VW Golf AllTrack and getting responses about having to clean the intake valves after a while, I got to wondering. Why do diesel engines not seem to suffer from dirty intake valves like DI gas engines seem to do? I know that if you run the intake valve at a high enough temperature, the debris will not collect. Is that what they do in diesel engines? Are there other tricks up the diesel builder's sleeve to prevent intake valve deposits? After all, these guys have been running DI for decades. What gives?