It should fit the 2005 STI. It was the same part number from 2004 - 2006. I don't have gaskets for the system so you'll need to find them either with TurboXS or another aftermarket provider. I have another individual who wants the system as well and I'll tell him the same thing... I'll take $500 cash. The first person who is able to pick it up can have it. Let me know what you would like to do. Thanks!