I was checking int to UPF48R filter and found this 2008 link
http://www.teamzr1.com/ubbthreads/ub...at&Number=2677
Basically the difference is a higher burst pressure rating, the internals are the same as the PF48 (Presumably migrated to the "E" non-metallic cage as the PF48E)
Derived for the LS9 engine, higher flow rates and higher pressure