I believe so. They only played Germany once, on an Easter Rock Festival tour with Thin Lizzy, Nazareth and one other band, it might have been Sabbath in the last throes with Ozzy. I assume that was when Lynott and Nauseef got to know each other. IGB made headlines for devastating a buffet backstage and blaming it on their roadies. Knowing that Fenwick and Gustafson were notorious practical jokers especially, my bet is on them though.
I admire you for having seen them! I wanted to go, but didn't have the money! For all their clever-clever jazziness, IGB were live a force to be reckoned with. They could actually play that stuff live.