Have you pulled the heat shields off to see where the leak is yet? You may be letting yourself in for more grief than you need, to plan a swap if it's something easy to fix. If I remember right there were a bunch of heatshield fasteners gone already. Think somebody had a look and buttoned it back up? I found some nifty stainless hardware to replace the rusty bolts on my heatshield. I haven't put them on yet but I think they'll look cool.
Talk to Rouge if you are thinking about paying someone to fix it. http://www.miatasolutions.com/