"Performance tweaks" refers to small changes or adjustments made to improve the overall speed, efficiency, or functionality of something, such as a device, software, or system. Full definition
There are a lot of great changes here, as well as a host of bug fixes and performance tweaks for console and PC players alike. (shacknews.com)
The cars are light, compact, and, with the exception of the requisite safety equipment and a few performance tweaks, are basically showroom - stock. (topspeed.com)
A lack of true performance tweaking and additions makes this a rather hard sell on the 3DS, but it's certainly not the worst version of the game out there. (metacritic.com)