Yahoo Message Number: 54803 (http://groups.yahoo.com/neo/groups/Country-Coach-Owners/conversations/messages/54803)
We had the same problem on our 99 Intrigue. It was also caused by improper sealing of the engine compartment, allowing diesel soot to get inside. If I'm not mistaken we used a mixture of Oxyclean and water in a spray bottle to get rid of the stains. To be sure go back a couple of years in posts on this site and you will find many posts concerning this issue. Actually you could probably type in ceiling black marks in the message search area and find the posts. Hope this helps.
John Flynn
05 Allure 31143