Fuel Fluke

I have a few thoughts..

A mechanical pump has very little in terms of "suck" to it. So IMO, start with basics. Is your tank or gas cap is vented properly? (easy tet is pull the fuel cap after it's been running a while. If you hear the hissing of air entering, it's not vented well enough...)

Pulling thru an electrc is not a good idea. If you need a pusher pump (the elctric is out back by the tank, correct?) then run it all the time. Although if you have an electric, I would not have bothered running a mechanical at all. The block off's cheaper than a pump :D.

The routing of the line is odd. IMO, it should not ever go up over the inner fender bulge and then down to the pump. You are asking for air bubbles in the feed side that way. The heat is a non issue. If there is 1.5" of air there, it's not picking up any heat from the headers and you placing a finger on it and feeling cool is the indicator. The fuel inside will be no hotter than the outside of that line.

The fuel all inside the carb bothers me. Because any carb that is starving will be dry in there. Kinda makes sense, no? No fuel inside the bowls = no fuel...

It should not be idling as high as it is. I dont know the package or your tuneup. But if the thing hangs up at 1100, your ignition curve needs some work. If you can't get it to idle at 800 or less, especially with a stick, your carb needs work after you fix the distributor.

I think it's a combination of these that are giving you fits.