Dennis Hogan runs 9.90's @136 through three mufflers. Two under the rear seats, and a dual pass cross flow Walker Ultra Flow behind the rear end. Straight through mufflers (Ultra Flows) and 2.5" mandrel bent stainless. The car is church mouse quiet. (Only at idle/cruise). And there is no drone. Anyone that says their system doesnt drone must be deaf, LOL. Dennis spent a fortune trying just about EVERY system and muffler out there. I even wrapped the entire system from cylinder head port to,the tail pipe exit. Did nothing, 3" ultra flow where the cat resides, NO IMPROVEMENT, The only muffler that quieted down was a stock Riveria muffler, but it killed performance. We hung weights trying to tame drone. The ONLY thing that worked and didn't KILL power output was adding the cross flow muffler. On his race car he had a 3" version built, and that car ran 9.0 @ 149. Search for three muffler system and you can find pictures.