In large saucepan, whisk together pork broth, brown and yellow mustards, honey, horseradish, ketchup, brown sugar, garlic, salt, pepper, and cumin. Cook over medium heat until blended and simmering, then continue to simmer to reduce the stock, about 20 minutes. Prepare the grill for moderate cooking. Slowly grill pork tenderloin, turning frequently to prevent burning while brushing the Island Sauce over the meat with each turn. Slow grilling usually takes about an hour over low heat. Just before removing the completed pork tenderloin from the grill, place pineapple rings on the grill grates to warm through. When warm, layer the pineapple rings over the top of the pork tenderloin, and finish with a final splash of Island Sauce. Slice to serve. Posted to dailyrecipe@recipe-a-day.com by Recipe-a-Day on May 23, 1999, converted by MM_Buster v2.0l.