If you have the original fuel lines, those are pretty weak and prone to collapse.
High pressure line is better, but since it isn't formed like OEM you have the problem of it kinking when the tank is down. You'll probably notice this most when it's hot and you go over bumps. That's when it's most likely to cut out. When I had the external with the K&N fuel filter, I ended up running long line from the pump to the right, around the frame and back to the fuel rail and tank.
It worked great till I got hit and ended up replacing the tank with a 2001 when I repainted it.
are the lines noticably soft when you squeeze them if its that?