Framerate issue on power station

[Vtin]

Reinstall the game, reload previous saves or ask for a save past the area.

I have exactly the same trouble, that level is unplayable due to the slow framerate. Graphic settings lowed with no result. Loading from previous save spots doesn't work. Is there any way to download the game again in order to reinstall it? (and... ¿does anyone know if that will work?)
2011 Mac Mini 2.3GHz with 8Gb Ram DDR3.
Thanks!
V.