In a small bowl, mix together the chili powder, cumin, garlic powder, onion powder, salt, and black pepper. Rub the spice mixture evenly over both sides of the chicken breasts. Drizzle with olive oil and lime juice, then let marinate for at least 30 minutes (or up to 2 hours in the refrigerator for more flavor).
Preheat a grill or grill pan over medium-high heat. Once hot, add the marinated chicken breasts and grill for about 6-7 minutes per side, or until the internal temperature reaches 165°F. Remove from the grill and let rest for 5 minutes before slicing.
While the chicken is resting, prepare the grilled pineapple salsa. Preheat the grill to medium heat. Grill the pineapple slices for about 2-3 minutes on each side until caramelized. Remove from the grill and chop into small pieces.
In a bowl, combine the grilled pineapple, red onion, cilantro, jalapeño (if using), and season with salt and pepper to taste. Mix well and set aside.
Warm the tortillas on the grill for about 30 seconds on each side or until pliable.
To assemble the tacos, place a few slices of grilled chicken on each tortilla, top with the grilled pineapple salsa, and serve with lime wedges on the side.