Excavator repair: No Power, Stalling, Fuel tank and Filters. Yanmar ViO-50

My Yanmar has a problem where it loses power and then stalls. It's worse the higher the throttle is set. I've tried running it with the fuel cap off and that made no difference. Changing the inline fuel filter helps for a while, but then it happens again. What can I do to fix this thing?

Addressing some questions:
Why not use rust remover? Haven't heard of that before, and won't it just rust again? I didn't want to experiment only to find that I somehow made the problem worse. Are all rust removers compatible with diesel?

Magnets? Would certainly help, and I may do that if I continue to have problems. But they would require cleaning periodically. Would have to remove the side panel, and then the sending unit every time to clean. I could put a magnet on the side of the filters. I've never tried that before.

Why didn't I put the second tee in the other orientation so both filters have a 90 degree turn, equalizing the bias? Because I'm an idiot, that's why. I should have thought of that, and will do so. ;-)

What about electrolysis? Never thought of it. Cool idea, but it would also just rust again.

But you didn't really fix it. True, but that's the nature of owning and running machinery. You have to pick your battles, and choose where your time is best spent. To really fix this, I would have to remove the fuel tank and apply a tank lining product that should be a permanent fix. If it continues to plague me, I will probably do this at some point. But it would be many hours of work just to get that tank off.

Were those really sparks? Apparently some people think it was just light reflection. I don't think so myself, but I guess it's possible. I tried it twice more to see if I could repeat it and with the same camera and light setup, I didn't see the same result. I filmed sparks before, and that's exactly what they look like in freeze frame.

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