i currently have a ss induction growler kit on my gen 3 calais i was wondering how much of a power difference there would be to swap it for a otr and also would it need to be retuned
OTR would require a MAFLESS tune in most cases, and you'd expect around 225-245RWKW from OTR, Exhaust + extractors + tune.
You'd see a big increase I would assume.