Yeah, it was an "oh no what have I done" moment when I started it up the first time. Going down the street was embarrassing. Sounded like a trumpet on roids. But after a couple freeway hours, it has become much more appropriate sounding, and I'm sure the hi flow cat is adding some forgiveness.
I don't have my CEL delete tune yet, but the e85 burns so clean that I suspect the computer doesn't detect anything is afoot, so no codes or warning lights yet.