Peel the red guavas, and cut into large pieces. Add the guava and tomatoes to a food processor. Pulse until relatively smooth. Push through a metal strainer to remove the seeds. Set aside.
Over medium heat, heat the oil in a medium saucepan for 2 minutes. Add the garlic, ginger and chili, and sauté for 3 minutes.
Add the guava and tomatoes and cook for 5 minutes, stirring frequently.
Stir in the juice of 3 limes, vinegar, soy sauce and brown sugar. Bring to a boil, then lower the heat.
Simmer until slightly thickened, about 15 minutes.
Serve with wontons, sushi or chicken wings.
