Terry Houston Downpipe Leak

[89TTA1415]

I just bought a Turbo Trans Am and I have the 3" THDP with the separate turbo elbow and downpipe where the downpipe goes into the elbow. It leaks quite a bit and I'm wondering if anyone has a fix for this? I have tried moving the clamp band back and forth but it still leaks. Is there a piece that I'm missing as I only have the clamp with the two bolts through it. Any insight into this would be most appreciated as I know this same setup is used on the turbo buicks. I was just doing some research and notice that the new downpipes have a collar where the elbow goes into the downpipe. On my version the elbow actually goes over the downpipe. Is this normal as that is where my leak is occuring? Thanks...