Our old coach, a '96 Allergo bus, had evenly spaced stains that went across the ceiling about four feet apart. We tried various chemicals and techniques but nothing worked. While at Red Bay in the service area, I inquired about a solution and was told that the ceiling carpet was permanently stained and nothing would work. I cut oak strips about 1/4" X 3" X width of celing and stained them to match the cabinents. Covering the stains was a good solution. Good luck with yours, Bob