2004 379 Pete. Can’t get fuel tanks to feed equally.

Sandman,
So I’ve got fuel problem on a 2004 379 Pete, 500 acert cat.
Fuel only feeding off passenger fuel tank, keeps left fuel tank overfilled constantly spewing out of cap vent. All new feed, return lines, tank vents, splitter valve replaced 4 times, new pickup tube in driver tank, still having same problem. HELP!!!