I know that Koffi and Jean Goubald were close in the early 2000s and I have heard Jean Goubald praising Koffi's artistry in terms of his writing and playing of the guitar, but did they ever collaborate?

jean goubald says that he wrote a song for koffi but koffi still did not sing it for years maybe its too technical for his current voice who knows

Man, so Koffi must have many unreleased songs by the sounds of it.