I had similiar issues on my 383 I used the carter street pump strip pump and the stock pump all new and tried multiples. Back in the 90s I never had a problem it wasn’t until around 03 04 when I had issues. I changed the lines filter pu tube and rerouted always from hot sources no fixes found. I did more research and and poked around with my heat gun and found out the pump was getting hot on the side of the block 190 200 etc. normal motor temperatures .Herre’s the problem E10 or E15 boils at very low temps 150 160 180 so no matter what you do the pump will boil the fuel and vaporize inside. It’s the fuel we use and real fuel boils over 200.