For 2016-2018 Trax's, there are a few "universal fit" modifications you can make, such as:
chambered/turbo exhaust mufflers
exhaust tips
premium aftermarket air filter
Of course, people have mentioned custom performance tunes, which can boost HP/torque significantly, and increase fuel efficiency. With only the above-mentioned add-on's, gains are minimal, but will give it a growl and get you some looks. I did notice there is a company out there which designs a custom-fit valvtronic dual catback exhaust system for the Trax, but it's special order and they don't list a price (most likely it'll cost your arm).
For the pre-2016 Trax, you could conceivably retrofit air intake, exhaust, and blowoff/recirculation valve systems designed for the Cruz 1.4 EcoTec turbo. Inside the Trax engine compartment and chassis, there's not much room for play, though. It's slim-pickens for us, folks!