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!!!

 

I've been reading prior threads on here about this problem and I'm going to start my own diagnostic by taking one line at a time off from splitter and top return on tank and blow pressure through to make sure no blockage. I'm going to do the return to passenger tank first seeing nothing comes back to that tank. Then next my feed line from left tank to 3 way feed fitting. So on.
If anyone has a better idea or cure for my problem, I'm open to all information and would really appreciate your feedback.
Thanks, Sandman.