I finally get the legendary PC-9801-86 ! I found it for 11.000 yens ! (around 100 $). With full set : box, manual, card, cables. The card is in perfect condition ! No rot, or bad soldering. I did some quick test, and she worked with all my games ! And especially Policenauts that I could finally get it working with lip sync! I am so happy!
You can see pictures and information about the board in the PC-98 sound card section : here.