Dyno test for XForce’s Stainless Steel 3-inch Cat-Back System | 2017 Subaru WRX STI Exhaust Shootout 

We will try to see if we can do a longer video. In the meantime, this might help you. dsportmag.com/the-tech/showcase/2017-subaru-wrx-sti-exhaust-shootout-xforces-stainless-steel-3-inch-cat-back-system/

And this is a comparison with a few systems. dsportmag.com/the-tech/2017-subaru-wrx-sti-exhaust-shootout/

Summit racing did a dyno pull on a Coyote Mustang and the difference between open and closed was 40whp. If it’s that restrictive on a NA setup I can only imagine how bad it is on a forced induction engine.