My Diced Pork Is Cubes Of Rubber

It might not suit the dish all that well, but if you want to go to the trouble of removing the pork and slicing it very, very thin it might mitigate the toughness, I’ve done that with overcooked pork tenderloin and then repurposed the meat in say, a noodle salad, ramen broth or a sandwich, and although it’s still not as good as perfectly cooked pork, it was better than leaving it in larger chunks.

It rather depends on where on the critter your pork cubes came from. If you cut them, or they were cut, from the tenderloin, or regular pork chops- the meat is simply too lean to cook for long. It dries out and tightens up, and there isn't a lot you can do for it. Pork cut from shoulders will have more connective tissue and fat, and being rubbery is a sign it needs more cooking time. What I suggest you try next depends on what you have equipment wise. If you have a pressure cooker or Instant Pot, I recommend about 20 minutes of cooking at high pressure. If you don't, then try baking it covered in the oven, at about 325F, for an hour or so- adding more liquid as it's needed. Hopefully your cubes are cut from a shoulder, which should give up and tenderize. If not, well, perhaps you could separate the meat and give it a good chop up. You won't have cubes anymore, but it will at least be in smaller and easier to chew bits.