Nrad2000; sometimes a Clanky sound comes from my Saito when it goes lean, low tank level and nose up.
Not sure about the fuel draw of a YS, but am sure lean is not good. The worst plane I had for this problem had an extra 6" fuel draw.
By that I mean the tank was a good 6" from the firewall.
I either run it richer, or do the nose up stuff in the first half of the flight!

PS, after thinking about your case, another way to lean out is foaming of the fuel... is your tank "soft" mounted in foam?
I think you said your YS is pumped, so faoming or a fuel line split is more likely to lean out a pumped YS than how far you draw fuel.