In a large bowl, mix pecans, pine nuts, pumpkin seeds, pistachios, and oil. Add sugar, 3/4 teaspoon chilies, and 1/2 teaspoon salt; mix to coat nuts evenly. Add more chili and salt to taste.
Coat a 10- by 15-inch baking pan with cooking oil spray. Spread nuts in pan. Bake in a 325° oven, stirring occasionally, until nuts are browned, 15 to 20 minutes. Cool. Serve or store airtight at room temperature up to 1 week.