Bolting on an Invidia up pipe means setting your car's exhaust system to a higher level of performance. The factory exhaust setup in conjunction with the catalytic converter is not meant for gains in velocity or torque. What an Invidia up pipe does is bypass the cat in favor of letting the automotive exhaust flow with more freedom in an effort to unchain some of the hidden performance your car is capable of. There are many aftermarket exhaust mods, but choosing a Subaru turbo uppipe is often a priority for serious tuners.
The turbocharger needs efficient exhaust movement for the turbo to spool adequately. Stock exhaust systems disrupt this process. Installing an Invidia up pipe in place of your stock pipe eliminates the restriction holding up performance gains by freeing up the flow more efficiently. Even if your Subaru WRX or STI does not have a stock performance up pipe, you can still customize. An Invidia turbo up pipe can be an addition, not just a substitution. It will mate with any turbo that can be mounted to the existing auto exhaust uppipe.
Improvement in performance varies with a turbo up pipe. There are dyno tests done in different environments that will display a discrepancy in numbers, but it ultimately depends on variables such as how old your model is and what kind of exhaust components you may have already installed in addition to the Invidia up pipe. Generally, you can expect a jump between 7-10 horsepower along with quicker turbo spooling. Overall throttle response should be more agreeable with a turbo up pipe, as well. Following installation, you should notice your turbo spool time to hit at approximately 5-600 RPM sooner than before.
Invidia uppipes are crafted from T-304 grade stainless steel for max durability and also include replacement studs to aid in a more convenient installation. For drivers concerned about a CEL fix, Invidia uppipes feature a built-in EGT bung to correspond with the stock sensor. For later models assembled without an EGT in the OEM pipe, you can use a plug for the new Invidia uppipe (not included).