I bought an S70T5 years ago, the po got it off a guy in Sydney who had a 4" on it FFS.
It had head trouble so he bought new head, it was flawed, second new one same, third time lucky , it had some ecu upgrade we couldn't pick but he had a 3" system on it that he had made , sounded ace , went like a train and sounded nice, it's one I should have kept but sedan vs wagon........