Bought My Third Car - It's a Suburban - BIG Picts Too !

[Electronic M]

So it's been pretty good since then. One of the tail gate gas struts failed and got changed. The transfer case rear cover corroded a leak hole from the outside in and I had the FUN of pulling the transfer case and swapping the cover... Discovered the transmission rear main seal was leaky but instead of fixing it or properly replacing the gasket between the transmission and transfer case that stopped the rear main seal from leaking onto the ground I put it back together and have been adding around a quart a month to it...I need to fix that this summer.
My rust repairs are starting to bubble so I'll have to address those again.

But what's really driving me nuts is a fuel system problem...A few years ago it used to be that on -20 winter days if there was less than 1/4 tank it wouldn't start because it wouldn't have fuel to the injectors. It's gotten to the point it won't start at any temp if there's less than 1/4 tank. Now if you start with more you can drive it to a hair above Empty and it'll be fine, but if you park it for a day even with 1/8 tank it won't start till you add 2-5gals. Anyone ever seen this before on this era of GM truck?
I'd like to find the root cause rather than load up the parts cannon.