Here is one other place I varied from the installation instructions. Notice the stock speaker wires (the ones that would normally plug on to the speakers). They must connect to the audio input feeds from the center of the power control unit.
The install guide would have you make this connection with a butt connector. I didn't want to cut the stock harness to make the splice so, instead, crimped male spade terminals on the leads from the power control unit. This allowed the speaker wires to plug on to the audio input leads but did so without cutting any stock harness points on this bike. Because of this the unit could now be removed from the bike at any time, the original connections all put back as they were, and nothing would look like it had ever been there.
Aside from the speaker wire to power control unit connections seen here also see the speaker outputs from the amplifier units themselves to the speakers themselves. Again, this is mirrored on each side of the bike. Be sure you keep proper polarity on all the speaker leads.