I have Dynomax Ultra Flow Welded mufflers (dual) on my 95 Grand Prix with no cat, 2.5" mandrel, and a Dynomax bullet resonator. It'* all straight-through (no baffles) and it'* a really obnoxious sound. Nice and deep, people really turn and look, but not refined at all. At WOT, the 3100 (238WHP, headers) sounded like a pissed off chainsaw, and the Series 2 L67 (stock, manifolds) sounded a little better but still raspy and obnoxious at times. I will be scrapping the whole thing soon when the Series 1 goes in, and deffinitely going with baffled mufflers.