I'm starting to tune my stock engine ft-21 allroad and have been chasing a rich LTFT issue.  Fueling is 550 ev14 injectors (0280158117) @ 4bar, stock lines and walbro 450 pump in the stock housing.  I have high fuel pressure (around 5 bar) that drops back to normal when I disconnect the return line at the tank hat and let it run into a gas can. So It looks like the return system in the tank can't handle the added volume.

I know many have ran this pump in stock lines (but probably not many with injectors this small on gas) and I never heard of anyone having issue.  Has anyone seen this before?

I think I ruled that out, no change when venting the tank to atmosphere. 

I just find something interesting though, while running into a gas can I ran the tank down to about 1/8 full. When I hooked the tank return back up FP had dropped to 3.5-4 bar, but was bouncing around alot.  Put 2 gal back in the tank and FP was back to 5 bar rock soild.

Yea if you call the Nissan hotline or your local dealer, they will replace the fuel tank with a new version.

How big (or small) is the restriction of your FPR? Not all FPR have same dia restriction/return. If too small, pressure at injectors could be more than nominal.