Saddle tank fuel pickup tubes

[Cabnchassis]

91 R3500 6.2 diesel

Changed the sending units/pickup tubes in my truck and I'm getting air in the diesel whenever the truck dips under 1/8th of a tank. Is it possible the parts store pick up tubes I installed were too short? I haven't been able to use the passenger side yet so I'm just wondering if anyone else has had this happen? Any other ideas why the top 7/8 of the tank runs great and the last 1/8 picks up air, surges, and sometimes even dies? Lift pump is brand new btw.

I've been busy and I have to drop the passenger side again because I didn't clean it when before I installed the tubes (like an idiot) and it's been sitting under the truck unhooked from the filler sort of open to weather for quite a while.