The eight-car sets of R160 (the 83##-84## series) were initially put on the J/Z and L lines. On the L, they replaced all the remaining R42 (which were staying there for a while due to an increased ridership). On the J/Z, they primarily served part-time az Z trains. They are still running on the L (along with R143, which are still the majority). However, a few months ago, the R160's were moved from J/Z to M. Why? It doesn't make much of a personal difference to me. But I would still like to know why this happened.