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how do I unclip the cable wire from the porsche cayenne horn once I have actually accessed the horn and unbolted it?

there were a couple of different plugs

slide lock:

carefully inspect the plug & see if there is a "slide lock" under the tab that would need to press at the end of the plug.
If so, the "slide lock" needs to be pushed out, then the tab can be pressed

No slide lock:
press the tab down & pull plug out

No tab:
insert a small flatblade in top of plug to release the female part of the connector from the male (wire side) connector