Mike, we have been breeding ASFRs for almost 2 years. I bought a couple of trios in late spring of '06 and we now maintain 10-12 trios in addition to our mice and rats.
They have been feed only Mazuri 6F, except for an occasional treat of sunflower seeds. I know that doesn't quite fit the definition of exclusive, but their diet is over 99% Mazuri 6F.