and a subi will loose that sound if you put equal length on it
The "equal length" thing is urban legend; you can make any I4 engine sound like a subie by pairing two adjacent firing cylinders into one outlet. Tie 1-3 and 4-2 together and send them out ina dual exhaust and you get the same pairings as left and right banks on a sube (or VW, Lycoming, Continental, or Porsche) flat four. Even a Honda Gold Wing makes that sound and they typically have very equal length pipes.
Back in the day, Porsche 356 racers used to cross the exhaust to get rid of the adjacent exhaust pulses. That makes a 356 sound like an inline 4 with tri-y headers. And the 4 into 1 stingers (equal length) loses the distinct flat four sound, too.