In a large pot over medium, bring water to a boil. Season with salt, and add macaroni. Cook macaroni until al dente, around 8 minutes. Drain and set aside to cool. 

In the same pot of boiling water, place chicken breasts and let cook until cooked through. Remove from the water, and let cool until cool enough to handle. Using two forks (or your hands!), shred the chicken. Set aside. Reserve 1/4 cup chicken stock. 

Make the dressing: In a large bowl, mix mayonnaise dressing, crushed pineapples, ground black pepper, and reserved chicken stock. Season with salt and ground black pepper. Add cooked macaroni, bell peppers, carrots, and shredded chicken. Toss well. Serve while warm or chill until ready to serve.