MPS stands for "Master Printmaking System" (http://www.piezography.com/PiezoPress/piezography-products/mps/), which is what we used to refer to our Selenium (SEL) and Warm-Neutral (WN) glossy printing system, which were originally the only glossy compatible Piezography inks. Now (since 2012) ALL Piezography ink tones are MPS, in that they are all both matte and glossy compatible.
For Selenium inks, you can use SEL or MPS curves, though Piezography ink tones share such similar ink densities, that you can likely use curves for any Piezography ink- as long as it's specific to your printer model and paper (or at least very close to the paper you're using) to get very good results. Please note the glossy curves we have available are custom curves made for different customers over the years, and checked/confirmed to be good, so others can use them, but everyone's printers can differ, so if you don't have great results with the glossy curves we have available, you can get a custom curve specific to your exact printer/ink/paper/computer setup to optimize the results for your specific setup.
Best regards and happy printing~ Dana