Tyros
This is from Flame's website. Doesn't really say what happens if you add a high level NPC to the party but useful info on chest drops and how level sensoring works.
However, reading between the lines I think Xfactor may be right, it depends on the highest level in the party.
Click on Item Index and then on Chest and Drop List explained or on Level Sensor Chart.
http://www.flamestryke.com/wizardry8...trykes_w8.html