Any Other Suggestions...

What size fuel line do you use? Might sound crazy and be pointless but i remember reading awhile back that some people who ran the 1/2" line for a drag car could have this issue because when launching the fuel wants to stay where it is in the line or even go backwards, cant remember who wrote the artice but they reccomended going to 3/8" line if possible to help relieve the issue because with more volume of line needing to be filled on hard launches the pump cant keep up. As an example if you go from 1/4" line to 1/2" line your actually tripling or quadrupling the fuel volume instead of doubling