Did a bit more investigating, there is no fuel tank access hatch sadly. Also while underneath, a couple of my fuel lines looked REALLY greasy, and something really peculiar caught my eye.
First there isn't much around there that could cause this sort of greasiness on the line other than fuel.
Second, If you look in the picture below, there is a hardline with a rubber sleeve around it. At the edge of the sleeve on the hardline, it looks clean all the way around. I took a microfibre to it afterwords, and the rubber sleeve didn't move too easily, so i'm thinking the only way that spot could be clean is if there was a hardline leak inside that rubber line causing fuel to leech out. Will investigate further. Maybe while i was wheeling a rock shot up and hit it.
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What area of the vehicle is that? I'd most certainly focus my attention on that spot. That is how diesel leaks look. If you're leaking diesel that bad, then it'll definitely be drawing in a lot of air into the fuel system. Could easily be causing all your problems.