Beginning after the secondary catalyst, the Touring Edition picks up right before the rear axle and provides a full single 3" route from this point and splits to dual patented drone-canceling 180 Technologyª resonators, followed by 3" tip outlets. Given the straight-through design and lack of packing material, the 180 Technology resonatorsÕ job is to defeat drone prone frequencies that would otherwise be experienced within the cabin. Maximum flow is maintained and exterior volume is increased with the interior experience being much more sophisticated and tame. Which option should you go with? Due to the structural differences between the 330i and 430i, we recommend the following configurations: 330i: With all factory emissions equipment in place, the Track Edition is recommended for those wanting an elevated exhaust experience from within the cabin. If you plan to upgrade anything further upstream, consider the Touring Edition. Otherwise, the Touring Edition will resemble stock from within the cabin. 430i: Given the coupe design of the 430i, interior acoustics differ when compared to its sedan sibling, with new frequencies making their way into cabin. Due to this, and with all factory emissions equipment in place, we recommend equipping the Touring Edition to ensure an enjoyable driving experience. Drivers can, of course, equip a Track Edition, but it may be much for some, especially if anything upstream has been changed. YouÕve been warned.