Ooms

Yes they were "aftermarket" lower flow cats. Being in California, one is not allowed to purchase catalytic converters at all, nor install themselves. One must go to a CA certified muffler/exhaust shop. I wanted a cat just like I had but was told that those were no longer legal for the past 2 years, even though they had some old stock just like the stockers from before the law change.

GTHMH: After searching the forums, it does seem that Audi deems SOME backfire on engine braking normal, and yes, it was very annoying. Now, its all but gone away. Sometimes just a little, so very little "pop", but I am ok with that.

On a side note, the shop said it would be legal to change my muffler. On a 12v engine, what would sound the best mfg for mufflers? Not ricey, just a little more throaty? I lost a little throaty sound going to a lower flow cat :-(