What els will cause low Full pressure? running 20-30 psi needs to be 55psi up.

I got the 2nd pump E3270N at Advance Auto parts. Do you think the 2nd clamp will cause a lose of 25PSI?

i understand,you got it at Advance,but it's still an Airtex.when i replaced my pump,i used both clamps.either way you are going to either drop the tank or pull the bed off again to check that hose,or replace the assembly like pushrod said.you should check the metal lines on the assembly,cause you might find a crack or hole in them.and i don't see how they sold you the first pump for a 6 cylinder,cause there wasn't a 6 cylinder for a 1 ton truck.