Hi Linda,
That is a good point! Many pet owners feed their chinchillas bad foods because they don't see the immediate effects. We just have to do our homework and look to the ranchers for that info. Here in the USA chinchillas have been raised on ranches for years. Many of our current ranchers have been in chinchilla breeding for 20-40 years! Over the years they have learned what is best for our chinchillas and we as relative new comers try to learn as much as we can about what has proven safe and we stick to that!! We know that raisins are safe because chinchillas have been eating them for decades with no ill effects. We know that nuts, fresh fruits, and veggies are bad because we have seen their ill effects and we (chinchilla breeders as a whole) have researched the life of chinchillas in the wild and know that these things are not part of even a wild chinchilla's diet.
Just as with our own human diets we look to the experts to tell us what the healthy foods are, what foods will kill us over time through high cholesterol, etc, which ones help prevent heart disease...we have to look to the old-timer chinchilla ranchers to show us what is best for our chinchilla friends.
So it comes down to good research and finding a good mentor!!
As for dried pork ears, those are not good. Keep in mind chinchillas are not meat eaters so their food and treats shouldn't contain meat.