Welcome to my world! I too have that same fuse box on my 97' EB 4x4 4.6L. I was having the same problems with my running board lights. I tracked it down to the relay under driver side dash. 2nd relay from top on left side. It also controls the battery saver circuit. I have looked everywhere for explanation of these relays, but found nothing so far. I have a Chilton book for 97' - 03', but no mention of this relay block anywhere, not even in pictures. It may just be spare relay holder, but then again, why would it be wired if it was just a spare.