Combine mango, onion, cilantro, jalapeno, 1/4 cup lime juice, 2 T. olive oil. Season with salt and pepper and refrigerate for 2 hours.
Brush both sides of fish with remaining olive oil and lime juice. Sprinkle with chili powder, salt and pepper. Grill (or broil) for about 4 minutes on each side or until cooked through. Serve with salsa.