Many simply do not install the three way "Guitar/Mix/Synth" ON-off-On DPDT Switch
This leaves you with a guitar in the "Mix" position all the time, as long as you set the VG/GR/GP processor to "GK-2A"
else you must follow the steps here
GK-Kit Internal wiringhttp://www.vguitarforums.com/smf/index.php?topic=7893.msg56130#msg56130
I get no regular guitar signal through the 13 pin cable and some of the patches in the GR55 need it to sound realistic.
Remember the most important control when doing any internal GK install is the GK-VOl pot
If you omit the GK-VOL pot, then the connected VG/GR/GP 13pin processor will typically have all patches subject to the Patch Level control which is typically under direct control of the GK-VOL pot. if you omit the GK-VOL pot, you typically must to edit all patches you expect to use to avoid using the "non existing" GK-VOL control .
Read all posts in this thread Internal GK-KIT-GT3 questionhttp://www.vguitarforums.com/smf/index.php?topic=133.0
And read How to enable "Normal Guitar Pickups" and make the GK-3 Guitar/Mix/Synth three-way switch work with the GR-55:http://www.vguitarforums.com/smf/index.php?topic=3402.0
Which explains more details on the importance of the GK-VOL control pot.