Mom & Pop's Carolina BBQ Sauce

1 C prepared yellow mustard
3/4 C cider vinegar
1/4 C water
1/2 cup sugar
2 T chili powder
2 T brown sugar
1/4 C Mom & Pop's BBQ Pork Rub
1 14-oz can diced tomatoes

Combine ingredients and simmer 30 minutes.  Blend and refrigerate.