Walbro inline pump pressure problems HELP!!

[hubdawg]

72 Blazer with 2004 LS 5.3 with truck intake and fuel return line. I'm running a new walbro 255 inline pump with a inline filter in front of it. At the shrader valve on the fuel rail I get 52lbs of pressure when I crank or cycle the key and most say I need at least 58-60lbs. My truck wont run right and pops and crackles when I start it. I disconnected the fuel line on the engine side of the pump and checked pressure there....still 52lbs. Next I disconnected between the stock tank and the the pump and ran a hose directly into a full gas can bypassing the tank.....still 52lbs. Shouldn't this be pumping much more than 52lbs and be regulated at the regulator on the fuel rail. I put in a new Walbro 255 and had same results of pressure. So far I've wasted $120 on a new pump and would like to stop shot gunning parts. Any ideas?