I think the previous owner reversed the lines? as in he used the return as a feed and the feed as a return. Because the hardline that being used as a return is much larger then the feed line, which doesn't make sense to me. Is this a simple mix up near the pump? putting the wrong hose on the wrong hard line? Because of where the car is currently at, I can't get it up in the air to take a look at it. Not that it would make a difference, but the car is running a double pumper in it.

TL;DR pictured below. The top (larger) hard line with the threaded fitting is currently the return. The smaller diameter hard line on the bottom is the feed. Because of the diameter of the line, i'm assuming this is incorrect.

 

Yes, return line is 1/4" And pressurized line from fuel pump is 3/8". By reversing, the fuel supply is going to pressure regulator and then injectors? How can this run right? As boost pressure builds, pressure regulator is sealing, so injectors aren't getting flows.
something else is going on if it is running like that. Post a picture of your fuel rail and how the fuel pressure regulator is set up.
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Unless they got rid of factory connectors, you can't switch because the factory quick connectors won't fit on smaller return line.

 

The feed (threaded fitting) connects to the driver side of the fuel rail. The FPR comes off the passenger side of the rail and connects to the return line. Your description sounds like the lines are connected correctly. The FPR should be after the rail. If this is not the case on your car, post pictures, because it is a pretty large and time consuming f*** up to get all the way through swapping the lines without thinking to yourself "wow, this seems like it might not be right".