Any tricks for finding a leak in fuel line ?

Okay now I’m pretty confused , I temporarily replaced the rubber connections with some clear plastic hose just to see where the bubbles are coming from and at first no bubbles came up so I thought I was good. I took it for a drive and it sounded a lot better when I gave it some gas , but after a bit longer than before it started bubbling and hesitating and guess what, the bubbles were coming from the tank so I siphoned most of the gas out and took the sending unit out to check the pickup line for any rust or damage but the thing is SHINY brand new … I think my tanks pretty big and I was wondering if there’s only like 5 gallons in the tank would it not fully submerge the pickup line resulting in that bubbling ?