Cut each chicken breast half into four lengthwise strips. On each of eight 6-inch skewers, thread 2 chicken strips, 2 pineapple chunks, and 2 sweet pepper pieces.
For dressing, in a screw-top jar combine vinegar, water, salad oil, soy sauce, sesame oil, and dry mustard. Cover and shake well. Reserve 2 tablespoons of the dressing. Cover remaining dressing; chill until needed.
In a small bowl combine the 2 tablespoons reserved dressing and plum sauce. Brush over kabobs.
For a charcoal grill, grill kabobs on the rack of an uncovered grill directly over medium coals for 10 to 12 minutes or until chicken is no longer pink, turning once halfway through grilling. (For a charcoal grill, preheat grill. Reduce heat to medium. Place kabobs on grill rack over heat. Cover and grill as above.)
Combine the red cabbage and bok choy; divide greens among 4 dinner plates. Top with kabobs, pea pods, and mushrooms. Shake chilled dressing; drizzle over salad. Makes 4 servings.