The same folks who brought you Cardoc's supercharged H6 Outback.
Helpful threads:
http://www.subaruoutback.org/forums/110-gen-2-2000-2004/153114-gen-2-xrt-tuning.html
http://www.subaruoutback.org/forums/109-gen-3-2005-2009/150330-gen-3-xrt-tuning.html
http://www.subaruoutback.org/forums/82-vendors-playground-reviews/149769-gen-4-xrt-tuning.html
http://www.subaruoutback.org/forums/104-gen-4-2010-2014/146457-subaru-outback-3-6r-5eat-tuning-xtreme-racing-tuning.html
http://www.subaruoutback.org/forums/61-general-discussions/143289-subaru-tuning-affects-5eat-operations-performance-xtreme-racing-tuning.html
http://www.subaruoutback.org/forums/85-all-other-subaru-models/144689-subaru-tribeca-tuning.html
Helpful threads:
http://www.subaruoutback.org/forums/110-gen-2-2000-2004/153114-gen-2-xrt-tuning.html
http://www.subaruoutback.org/forums/109-gen-3-2005-2009/150330-gen-3-xrt-tuning.html
http://www.subaruoutback.org/forums/82-vendors-playground-reviews/149769-gen-4-xrt-tuning.html
http://www.subaruoutback.org/forums/104-gen-4-2010-2014/146457-subaru-outback-3-6r-5eat-tuning-xtreme-racing-tuning.html
http://www.subaruoutback.org/forums/61-general-discussions/143289-subaru-tuning-affects-5eat-operations-performance-xtreme-racing-tuning.html
http://www.subaruoutback.org/forums/85-all-other-subaru-models/144689-subaru-tribeca-tuning.html