Place fish in a plastic bag set in a shallow dish. In a small bowl stir together soy sauce, garlic, sugar, and ginger; pour over fish. Seal bag. Marinate in refrigerator 1 to 2 hours; turn bag occasionally. Drain; discard marinade. For charcoal grill, grill fish on greased rack of uncovered grill directly over medium coals for 8 to 12 minutes or until fish flakes easily (tuna may be slightly pink in center), turning once. (For gas grill, preheat grill. Reduce heat to medium. Place fish on greased grill rack over heat. Cover; grill as above.) Cut tuna into 1/2-inch chunks. Brush both sides of tortillas lightly with cooking oil and place 2 at a time on grill rack for 30 to 45 seconds or just until warmed.

In a medium bowl stir together sour cream and salad dressing. For each wrap, spread 3 tablespoons of the sour cream mixture on a tortilla. Place some of the tuna near an edge of tortilla. Top with some of the arugula, onion, and tomato. Fold edge over filling; fold in the sides and roll up. Makes 8 wraps.

To substitute one 1-1/2-pound beef flank steak, marinate as above. Grill directly over medium coals 17 to 21 minutes or until medium (160 degree F); turn once. Serve as above.