Thanks for the suggestions so far, they are really helping my troubleshooting.
In response the filter probably isn't clogged yet. I emptied out the tank completely, polished the inside to a mirror finish, changed the racor filter, polished the inside of the racor (though not quite as well) and poured clean recently bought fuel into the tank and racor directly. The problem happened immediately.
The bulb idea is a good one though my lines have swedged on compression fittings and are threaded on to the racor. No nipples.
I'll check the screen, lines and elbows now. Should have just replaced all the lines before I filled up everything but I forgot.