SUMMARY: tightened oil pump cable, engine ran poorly. loosened it to previous setting, runs fine. unsure if I should loosen it more (to factory setting)

I saw that the adjustment nuts on the oil pump cable had slack. Not knowing any better, I tightened the line (ie forcing more oil in at WOT). I noticed the bike was sluggish at low revs and was engine was dying. Normal for too much oil mixture?

I loosened the line and problem fixed, runs fine now. However, I found that even at the loosest setting, the valve is still much more open than the factory setting. It looks like the previous owner tightened it at the butterly as well. Is this strange?

I'm wondering if I should loosen it even more, to the factory setting. Or should I just leave it be. What's the ideal mixture, how can I check if it's adequate?