Welcome!! Congrats on the new 86! Looking forward to more pictures of your 86 and the build progression and your thoughts on how it compares to the A45 AMG!
Unequal length headers would be the best way to bring out that Subie/boxer rumble that you're looking for. I would recommend JDL, Tomei, or Borla for a high-quality UEL with a deep rumble.
-Sam