Most modern fuel hoses are non-transparent, so we don't get the misleading cues that happened in that case, Blue. Floating masses are really difficult to detect except when you flow the fuel fast, and they bunch up in a restriction. In the end they are usually removed by dismantling the pipe at every restriction point, then drying the pipe out and putting compressed air through it. I would say what you did in the end is an analogue of that.
Thanks for reporting back on exactly what was wrong, and how you finally found it Blue. It is a useful case for the archives, in several ways. I'll close the thread.
