Do I need a tune for a J-pipe on the 2022+ WRX?

Yes. Unlike a cat-back, a J-pipe is not optional-tune territory - it is a tune-required part, and this is not a case where you can run it for a few weeks and sort the tune out later. A J-pipe, also called a downpipe, is the section immediately after the turbo and it houses the primary catalytic converter. Replacing it is the single biggest change you can make to how the exhaust flows on this car, because it removes the largest restriction in the system. That does three things the factory tune was not written for. First, the turbo spools differently and holds boost differently. The stock map targets boost assuming factory backpressure, and with that restriction gone the wastegate control is working against a different set of conditions. Overboost is a real possibility on an untuned car. Second, the exhaust gas oxygen sensors see different conditions, and on a catless pipe the rear sensor no longer has a catalyst in front of it to monitor. The ECU notices. That is a catalyst efficiency code and a check engine light, and no amount of driving it out will clear it - it needs the tune to account for the change. Third, the relationship between boost, timing and knock margin shifts. This is the part that damages engines rather than merely annoying you. Catted versus catless matters for what happens next. A quality catted J-pipe - a high-flow catalyst from a reputable maker rather than a hollow pipe with a fitting - can generally run without a persistent check engine light once tuned, and gives you a fighting chance at an emissions inspection. A catless J-pipe will set a light, will not pass a visual or sniffer inspection anywhere that performs one, and in many places is straightforwardly not road legal. Know which rules apply where you live before you order, because this is the modification most likely to fail an inspection. On power, a J-pipe is the largest single hardware gain available on the exhaust side of a VB - genuinely worth having, unlike the cat-back behind it. But it is also the most expensive tier to do properly and legally, and it is the modification most visible to a dealer if you are still under warranty. A tune plus a J-pipe is an unambiguous signal that the car has been modified. The practical sequence: buy the J-pipe and the tune together, install the pipe, and have the tune loaded before the car goes back on the road under boost. If you are also planning an intake or a fuel system change, do all of it in one window and pay for one tuning session rather than three.