I called xforce head office today asking about this, they were fairly helpful. Apparently the dual 2.5" is around 92-94db and the single 3.5" is around 94-96db, fairly sure he quoted the stock to be around 84-86db. Also told me that if drone is an issue to go with the dual 2.5" but talking to exhaust shops they believe the 3.5 won't drone. Will probably just go the 2.5" dual stainless cat back as I can pick that up for $800 delivered over $1200 for the 3.5"