Preheat oven to 350°F. Brush both sides of tortillas with oil and with scissors cut each tortilla into about 5 randomly shaped wavy strips. In 2 large shallow baking pans arrange half of strips in one layer. (Strips should curl up on their own, but if necessary gently twist or fold them over.) In a small bowl combine chili powder, salt, and sugar and through a small sieve sprinkle half of mixture over tortilla strips in pans. Bake tortilla strips in upper and lower thirds of oven until just crisp, 6 to 8 minutes, and transfer to paper towels to cool. Make more chips in same manner with remaining tortilla strips and chili mixture.