Ya got me there - I'm only going by what is in the manual. However, reading the text, they appear to perform separate functions - as I understand it the filter check valve is part of the regulator assembly.

Right now I am trying to determine if the Bosch unit is equivalent to the MB - is it the original part supplier? The amazing interweb has a MB pump for about $500, a Bosch for $189 and some no name for $39. Heck of a range. Right now I am leaning toward the Bosch pump. In the mean time I am cycling the key to prime the system and reduce starter wear and tear.

HP