The Fiat 500 Abarth has only been on US roads for little more than a month and already there is a healthy aftermarket community and support network. Companies like 500 Madness, Hot FIAT, TMC Tuning and Romeo Ferraris have performance enhancements and accessories to turn the already potent 500 Abarth into a full out track car, a hot street ride or a comfortable tourer.
The Fiat 500 USA Forum has a full section on Abarth performance modifications. Make sure you visit it and see the latest projects.
Here are a few:
Forum member SLOABARTH's car is anything but 'slow'. See the thread: Started to modify my Abarth today (SLOABARTH's mod thread)
Member atxabarth's 500 Abarth also gets the treatment: See the thread: USA customized Abarth