I’m not sure that’s such a good idea putting the regulator after the filter, if your filter starts to plug you will never know and at some point the differential pressure across the filter will be high enough to push all the trash through the filter and now you have nothing to save the IP.
At work (I work at a brewery) the main filter in filtering is a DE (Diatomaceous earth)filter that can take over 80psi differential pressure and not bleed through but it can only do this as the filter can compact itself, the secondary 1um bag filter which is small enough to catch DE and yeast cells can’t handle over 10psi differential pressure without pushing everything through. Now I understand one filter is for beer and the other for diesel but differential pressure across a filter can not be ignored in either case.
Looking at the 6.4L powerstroke low pressure fuel system they put the secondary filter after the regulator.
The only time I wouldn’t worry about filter push through is if your pump either is weak enough not to be able to create a high enough pressure across the filter or you have another regulator after the pump to prevent high pressures across your filters.
Here’s how 6.4 works
Tank->primary 10um filter->pump with 24psi relief valve->3psi main regulator->secondary 4um filter->high pressure fuel pump or idi IP in my case.
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I would definitely have a filter before the IP after everything else in the fuel system.