Get a new tensioner here:
http://www.amazon.com/gp/product/B00BGBV8YY/ref=as_li_qf_sp_asin_il_tl?ie=UTF8&camp=1789&creative=9325&creativeASIN=B00BGBV8YY&linkCode=as2&tag=httpwwwyou00f-20
How to replace a SOHC Subaru 2.5l Timing Belt. This one is a 2005, but the process is the same for all 2.5L with the single overhead cams (one outside pulley instead of two).