A very common concern is whether the bike necessitates a fuel controller or ECU Flash whenever changing either or both the intake and exhaust.
The ECU has a baseline air/fuel config (called a map). This map is based on the volumetric efficiency of the engine. The O2 and other sensors take readings and make adjustments that are a percentage of the baseline.
When you change out intake/exhaust/etc, you’re changing the volumetric efficiency of the engine and because it’s a small engine these changes have a much bigger impact than you’d see in a car.
Now the sensors can only deviate a certain percentage from the baseline, so if you’ve changed volumetric efficiency too much you will exceed their ability to compensate and this will result in higher cylinder temps, detonation, etc. It won’t kill your engine immediately but you’re risking the long term health.
ECU flashes reconfigure that baseline map to be more “in line” with the volumetric efficiency of a modified engine so the sensors can do their job effectively.
In short, changing one or both of these primary engine components WILL change the performance of the bike. It is in your best interest for the sake of the bike’s longevity to have it “remapped” for the new parts. Do you have to? No. Would it be best for the bike? Yes. But the bike will generally be okay without remapping.