both systems are built the same in terms of muffler, resonator, and pipe size
the original has fully polished pipework and fully polished tips
the whoosh spec has brushed finish pipework plus Black Coated tips. We also include 3 free whoosh poly hangers
We are the #1 retailer for Thermal (ST market), they offered and we obviously loved the idea. The whoosh spec actually costs more to build in total but the price has been kept the same
As for the 3" adapter, selecting "YES" using the drop down menu is available with either kit
If you have a stock downpipe, select "NO".