Just do what i did Beau, My exhaust system is a full 3 inch with only a cat and muffler. When i get epad i have a custom pea shooter rear muffler which i chuck on which goes down to 2 and a 1/4 inch. Passed EPA with the full turboback 3 inch to that muffler, with only a cat and got 87db.
Know you have passed it now but me spending $150 on that muffler saved me 3 times already