I thought this picture might help if anyone is interested in the difference between a Legacy and Impreza's exhaust system. On the top of the picture is my '92 Legacy Turbo's stock exhuast from midpipe back. On the bottom is the exhuast system I used on my '98 Impreza RS. It consists of a Stromoung mid-pipe and Scooby Sport muffler. The setup I am going to try is HKS downpipe to stock midpipe (to preserve CC) to Impreza Scooby Sport muffler. I'll have the results next week.. I'm waiting on the downpipe.
The legacy's exhaust is longer all the way around. The midpipe is a couple inches longer, and the muffler is also a little longer.
If you would like details on my ongoing AT/MT swap check the following link. There is also a LARGER version of this picture on this page to show more detail.
http://www.shimmysideways.com/tranny_swap.htm