1. In a small bowl, combine the wasabi paste, soy sauce, vinegar, and mayonnaise. Set aside.
2. Brush salmon with olive oil and sprinkle with salt. Lay salmon on an oiled charcoal grill over a solid bed of hot coals or over high heat on a gas grill (450° to 550°; you can hold your hand 5 in. above grill level only 2 to 4 seconds); close lid on gas grill. Grill 6 to 8 minutes depending on thickness, turning over once, until just barely done (cut to test; flesh will be a darker shade of pink in the center). Remove from grill and quickly toast pita rounds on grill, about 2 minutes, turning once.
3. Cut or flake salmon into 1-in. cubes. Cut pita rounds in half and spread wasabi mayonnaise on insides. Fill each pita half with salmon, avocado, arugula, and tomatoes, dividing equally.
Note: Nutritional analysis is per serving.