Hi,
I replaced my mid section and back box with a stainless system from Subaru 4u.
I know its not the cheapest way to do it, but was WAY cheaper than Subaru OEM parts and gives it the proper noise . Went for 3 inch so not too noisy, just nice. All in All was £430 and went on easy (did it myself)
When looking for patern parts on ebay or other sites I couldnt find one that fit, or whoever I spoke to were not sure it would fit so just bit the bullet.
Im sure someone more knowledgable will come along and help, but I for the price I cant fault the product or the service I got from Subaru 4u