I have an 04 wagon I just put on a STi axel back and all of a sudden I have a really loud rattle which sounds like it is comming from the rear passenger door. Has anyone else had this problem? Or does anyone have a clue what it could be?

 

exhaust might be rattling against the under belly.
had a Borla Hush Cat back do this to me I got some Kartboy exhaust hangers (little longer and stiffer than stock) pushed itt just far enough down to stop the noise.

 

I have tried everything these last two days to figure it out. I was thinking of getting new hangers next and you just helped me decide.

 

I would order 3.
two for the muffler section and one more for the area near the rear axles.
you may only need the two, but it might not hurt to have the three.