Mix mayonnaise, BBQ sauce, water, vinegar and pepper in a large serving bowl until well blended.
Put chicken breasts in a large pot; add enough water to cover and bring to a boil. Reduce heat and simmer uncovered for 8 to 10 minutes or until no longer pink in the center. Remove to a cutting board to cool.
Add enough water to the pot to cook the pasta; bring to a boil then add the pasta and cook for 9 minutes until firm tender. Drain well.
While pasta boils, cook bacon until crisp and drain on a paper towel;cut into small pieces.
Add hot pasta to dressing in bowl and toss to mix. Tear chicken into bite-sized piecs and add to bowl with bacon, lettuce and tomato. Toss gently to mix.
May serve warm or cold.