Put a Dynomax Ultraflow 3" round muff on it...Much quieter...the Dynomax Race Magnum is a little louder than the Ultraflow but is still quieter than the ATR
I have the ATR 3" Single Shot on one of my cars and I don't find it that loud , but when I see a cop rolling beside me I sometime wish it was quieter. Dynomax ultraflow is a good compromise.
I read that if you have a 3" catalytic converter, the noise shouldn't be too bad...But I haven't tried it yet!...
By the way, those who want pictures of my fully polished ATR Single Shot, just let me know!...