Bought for dirt cheap used mazdaspeed dual muffler catback, but because it was used and cheap it doesn't came with the pipe that goes from cat to catback, so the question is will the pipe from OEM catback will fit to mazdaspeed's? From the photos they do look same

 

Only one way to find out but I doubt it. There was more than one version of the MS catback. But an exhaust shop shoudl be able to make it work either way.