Many varieties of sweet potatoes are sold in supermarkets. The sweet potatoes with darker skin (often labeled "yams") not only make a richer-colored dish, but also a tastier, sweeter one. The very light-colored sweet potatoes are not as sweet and are often drier.
Some meat thermometers are too top-heavy to stand up in a pork tenderloin. If the thermometer will not stand vertically, try inserting it almost horizontally, or sideways, into the pork. Using an instant-read thermometer is another option; check for doneness at the minimum time given. Instant-read thermometers are not ovenproof and can not be left in the pork during roasting.