Have a fuel filter en route; it'll hopefully get here some time next week. Given my recent
adventures in limp mode, I'm of the opinion that running some Diesel Purge through the upper fuel system probably isn't a bad idea.
Here's what I'm thinking: remove the old filter, do not reuse the fuel in that filter. Prime the new filter with Diesel Purge. Install the new filter, manually bleed and prime, start the engine, and let things clean themselves out. The fuel filter looks as though it can hold at least 500ml, so an entire can of Diesel Purge should be able to make it in there with room for some tank diesel on top of that.
Any reason why I shouldn't do this? I realise that the preferred method is to circulate the fuel feed and return lines through a separate container filled with Diesel Purge, but this seems to be more or less functionally-equivalent and without detaching the fuel lines.