Fuel pressure dropping while driving and under acceleration to zero at idle runs 4 lb electric Blue

I had a question with the Mallory 250 pump. It says if you take apart or disassemble the unit and put it back together to test the bypass pressure and adjust it between 13 and 18 PSI. How would I do that. Do I deadhead the regulator with a gauge and set the regulator or the? I'm sorry the bypass on the pump to 13 lb