I just bought my '91 GT a few weeks ago and it had the leak then. I sunk myself to the lowest level ever--Puddy. It leaks right where the headers go into the H-pipe and as far as I can tell there is no gasket. I'm guessing it just sits in there and the two are supposed to be mated up well enough not to leak...there's the story. Ask away, I know you tech-guru's need more info before you can provide your assistance. Thanks in advance!!