In the process of getting my truck to the dyno my tuner said I was questionable on fuel on the upper end . So I decided to go with the aeromotive pump with a wire upgrade . Got every thing together and decided to check fuel pressure ( 56lb ) . Should be 58 to 60 so I decided to change filter/reg with the wix 33737 being I am performance oriented on this build . I got 54lb . So I got another thinking I got a low rating one . Buddy of mine got me thinking about connections . He said the fuel feed is supposed to be the center 5/16 . I have my fuel feed on the outer 3/8 connection and the return on the 5/16 center position which I think a lot of people do an has worked fine for a few years now. On an average engine its not a problem . But those few lbs up top make a difference in fuel delivery and addimize the fuel . I have googled and seen it both ways but but unclear which is right . I looked on the wix site for instructions but I did not see any . The wix specs does say 5/16 inlet and 3/8 vapor .
Heres some pictures when I google and the wix site
https://www.google.com/search?q=wix+...HezlC9IQsAQIJA
http://www.wixfilters.com/Lookup/Par...px?Part=209876
If indeed the 5/16 is the feed this could be why the regulator is a few lbs low and not letting the reg work proper .