Tomasz Sobczyk focused on backend development for the GTNewHorizons/GT5-Unofficial repository, addressing a critical bug in the OverclockCalculator component. He resolved a numeric overflow issue in multiplier computations by migrating from integer to double precision, ensuring accurate calculations for large powers of two and preventing erroneous zero values in edge cases. This targeted fix improved the stability and reliability of high-overclock scenarios without introducing breaking changes to the API. Working primarily with Java, Tomasz demonstrated attention to numerical accuracy and gameplay tuning, delivering a well-scoped solution that enhanced the robustness of the backend logic within the project.