Welcome back? I figured you had sold the Supra? Welcome Back!
My guess is that you didn't get a great seal between the flange and the exhaust pipe. A crack is possible, but I'd take it all apart, clean and wire brush it and then put it all backtogether with fresh RTV sealant. I know that I'm still chasing a small leak in either my swim platform, exahaust or rudder -- but since I've rebuilt the FAE and flange several times, I don't think it's there any longer. My swim deck leaks FOR SURE.
Former owner of a 1987 Supra Saltare. Current owner of a Malibu 23LSV.