Sounds like you are convinced it is the IP. I don't think so. One bad batch of veg with water in it is not going to cause the problem you are seeing, especially on the Mercedes inline pump, where most of the moving parts are lubricated by engine oil, not diesel fuel. Usually you have less power on veg, not the other way around. Maybe you have an air leak when running on diesel? That could cause low power too. One way to diagnose that easily is to install a temporary clear pvc return line at the secondary fuel filter housing that returns to the tank. It should have clear, non foamy, no bubble fuel at all times, on veg or on diesel, engine running or not (as in overnight- where you should not see even a small bubble there).

I gave you 2 easy things to try first. Of course you can do the difficult thing first, like changing the IP.

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85 300D turbo pristine w 157k when purchased 167,870 July 2025
83 300 D turbo 297K runs great. SOLD!
83 240D 4 spd manual- parted out then junked