Exhausts these days have CATs? in, especially Impreza's. Most new age cars now have three CATs. Replacing these CATs with high-flow versions or removing them completely will improve performance.
The diagram below shows the location (1), (2) and (3), of all CATs in new age cars.
New Age Exhaust System Schematic
High-flow performance CATs
These are usually the best option however can be expensive.
Decat OEM pipes
This is an inexpensive way to decat your existing exhaust. You have two options:
- Purchase an aftermarket CAT replacement pipe or
- Decat your own OEM exhaust