Ah so many questions. That metal box with the vacuum lines is the remanance of the carb control module for the factory Mikuni carb - take it out completely. There are a bunch of electrical connections that hook up to it - ignore them. Those green wires in the fuse block? Those are factory fusible links - don't mess with them unless they are dodgy. The O2 sensor was also for the carb control - use it for an A/F meter