I have an 85 GSL with a streetport 13b and Holley 600. I have been running into fuel delivery issues which turned out to be a dirty tank. I replaced the stock tank with a 10 gallon aluminum fuel cell, ran 10 AN steel braided line from tank to 100 micron filter to brand new carter 4601hp, then 3/8 aluminum hardline from pump to brand new fuel pressure regulator (Holley 12-840). The pressure stayed at a steady 6 psi through all RPMs. I wanted to install a return from the regulator to the tank so I ran 6 AN braided line from the regulator to the tank. When I went to fire her back up, the car was running great but there was no fuel pressure reading at the gauge on the regulator. I know there was solid pressure still because I disconnected the line to carburetor and the flow seemed just as strong. I can't seem to figure out why the simple install of a return would cause a gauge to suddenly read no pressure. Any help would be greatly appreciated!

Shaun