I would like to intorduce the Aze Performance J Pipe for your 2015 - 2021 WRX/STI 
The Aze Performance J Pipes are fabricated  to replace your factory j pipe and its restrictive factory catalytic converter with larger 3 inch 304 stainless steel tubing, a freeer flowing G Sport  GESI high flow catalytic converter (or not) and available mounting hardware.
 
These Aze Performance J Pipes  are fabricated in Canada by utilizing local companies for their 304 stainless steel piping and mandrel bends, then they are TIG welding by hand with laser cut flanges. This is all done In order to allow the exhaust gases to flow freely without restriction to achieve highest possible power gains. All the while keeping all the OEM mounting points and bung locations for and easy DIY install.
*Propper tuning is required
 
Loose the weight of the stock restrictive exhaust, add some performance,  with a deeper sound and a perfect fit with the The Aze Performance J Pipe
 
-Made in Canada
-3 inch diameter
-304 stanless steel construction
-Mandrel bends
-1/2 inch laser cut turbo flange
- OEM bung location
-Hand TIG welded
-J-Pipe are availlable with or without a high flow catalytic converter
- An adapter is required for perfect fitment with the stock catback.
-A $40 shipping fee will apply