True,
I have BDR #291. I had an issue with a small leak in the S.S. gas tank. When I inspected the tank I found that when it was welded it was done with no backing gas (IMHO) this causes loose slag to form on the back (inside) of the weld. This may be what you are seeing. I've changed fuel filters three times in 7500 miles, each time there is a slight build up of crude in the filter.
Paul