John, saw this on subaruforester.org

"Headers/Cat-pipes and mid pipes are interchangeable between 93-01' Imprezas and 98-02' foresters. Exact same pipes, meaning any aftermarket header, high flow cat, or mid pipe for the impreza will bolt right up to your forester. Axlebacks are a bit different, as the impreza is shorter, so you may have to use XL exhaust hangers or get the tip extended to come flush with the bumper. Stromung makes a forester specific muffler, and some people are modding WRX and STI cat backs to fit. I would stay away from WRX aftermarket exhausts on an n/a subaru, as the piping is too big and you will lose power/torque. *06+ N/A subies have a different header/catpipe set up. The older style headers and HFC pipes will not work on 06+ subarus*"