I just went thru replacing an internal in-tank line that the hardware tuner decided to use an air line for. Obviously this was wrong. The line went hard as a pipe over time and I am not using E85 at all.

You should use a pure NBR line. No coating or any other rubber material or jacket. Just NBR. No NBR/CR as the common fuel lines are just that.

 

The Jeg's line won't work for a submerged line, its inner tubing can handle it but not the outer jacket - it would fail. PTFE seems to be the preferred hose however finding it is tough. Radium sells some, shipping is half the purchase price so forget that! XPR XT hose appears suitable, cannot find anyone selling it! I have Gates hose on the way but know it's not right and may try to reuse what I have but would prefer something I can put an AN fitting on instead of the efi quick connects. I'll check the U.K. company but would prefer to find something localish. Surprised Jegs and Summit don't seem to have anything, maybe marine supply?