In a large pot, bring 2 qts of salted water to a rapid boil over high heat. Add sweet potatoes and cook until they can be pierced fairly easily with a fork but still offer a good amount of resistance (8-10 mnutes). Drain, rinse with cold water and refrigerate until chilled (at least 30 minutes). In a medium bowl, combine remaining ingredients and mix well. Add the chilled sweet potatoes, toss well to coat. Can be kept covered and refrigerated for 3-4 days.