I don't know man. I watched the 1991 show in Indiana the other day.....and he sounded so bad on multiple songs.
It's a bit scratchy during that summer U.S. leg. No question.
Still some great shows in that leg though.
Listen to Jungle at Indiana. His voice goes out and sounds like it might be his last concert.
His voice changed so much between 1992 and 1993. There were always rumors of his having vocal surgery in this time. If you listen to say, WTTJ back to back at Paris 1992, and Argentina 1993, it's believable. Or YCBM.