In a bowl, stir together oil, chili powder, cumin, garlic powder, salt, and pepper. Pierce chicken breasts with a fork. Place in a large Ziploc bag. Pour marinade over chicken. Let marinate for 20 minutesl. Preheat grill on medium heat. Grill the chicken on both sides to an internal temperature of 160 degrees using a thermometer. Set aside to rest for 2 - 3 minutes then dice small. Warm the street taco shells on both sides on the grill.
Street Corn Salad:
In a bowl mix together all of the ingredients for the corn salad. Season with salt and pepper to taste.
Assembling Chicken Tacos:
Place the chicken on the taco shells, top with cojita cheese, and corn mixture. Garnish with cilantro.