FUEL PRESSURE REGULATOR FILTER

I was advised by my mechanic to lower the pressure from 4.5 psi to 4.0 psi using one of these MALPASSI FUEL PRESSURE REGULATOR AND FILTER:

http://www.glencoeltd.co.uk/malpassi-pro-fuel-carburettor-pressure-regulators/malpassi-filter-king-fuel-pressure-regulators/

Which model shall i purchase:

 or;

Malpassi 85mm Filter King With Glass Bowl 8mm Unions Product Code: FPR006

Need to get this sorted out today. Will appreciate any feedback in the correct direction.