In my experience with blocked fuel needles, 90% is trash in fuel. I have 2 fuel filters on my filler and the UAT is also a filter of some sort. As for the other 10% i think the FLUX used in the silver solder blocks the openings at the base. I have found that if you take a torch and CAREFULLY heat the base and the needle, not to get it too hot and blow through the fuel ring at the same time via a 4mm line it will unstop needles. BE CAREFULL as the needles get red-hot real fast.

You must be VERY diligent on keeping your system CLEAN especially when you first install it. Any small amount of plastic, silicone, tygon etc that is in those tanks WILL end up in the engine: ask me how i know [&o] Russ