What is a catless uppipe and what does it do?

A catless uppipe is an aftermarket component used in turbocharged vehicles, particularly in models like the Subaru WRX or Mitsubishi Evo. It replaces the factory uppipe, which typically contains a catalytic converter, with a straight pipe that eliminates this catalytic element. The primary purpose of a catless uppipe is to improve exhaust flow, reducing turbo lag and increasing performance by allowing exhaust gases to exit more efficiently. However, it can lead to increased emissions and may not be street-legal in some regions.