fuse box

Hi folks! My 2003 Blackbird has some electrical issues since I bought it. One of the PO mounted a security system before. But I think it make electrical things bad and he disassambled it. This is my opinion becouse I can see some modifications on harnes(both front and backside of the bike). OK...

The fuse box in my 1997 xx has space for a 3-pin diode (got the name from the on-line parts diagrams) beside the 6 fuses and the 2 spare fuses. The diode is missing but the bike seems to be running fine. I just ordered the diode 1. What is that diode for? :huh: 2. Why does the bike show no...