Hi I'm pretty sure Incorporeal immunity does not work in ToEE (vanilla and T+) as intended. Moreover it looks unfinished in vanilla. Essentially only positive, negative, force and ghost touch damage types should succeed normally. All other damages should have 50% miss chance. Immune against non magical attacks. The difference between normal miss chance is that incorporeal targets could be hit normally. But when calculating damage - miss chance apply for particular damage, if the damage is composite (consists of several different damages like 1d8 + 1d6 fire, etc).