Thanks for the responses everyone - I hadn't realized that the downpipes also contained a cat, which makes me feel much better about this whole thing. Real reason for me was going for the more straight out-the-back look of the AEW pipes. I tested them without the DB killer and also found them too loud, with it installed the sound is really quite good to my ears. Now to get through this break in period when the temps are barely above freezing so I don't need to wait for service in the warm weather!