In a large pot of boiling water, add the pasta and cook until just past al dente, per the box instructions. Season the pasta water with plenty of salt when boiling. When done, drain the pasta, cover and set aside allowing it steam and finish cooking.
While pasta is boiling, cut the chicken breasts into half inch cubes and season with salt and pepper. Cook chicken in a skillet with vegetable oil over medium high heat till browned and cooked through. Set aside.
In a small bowl, whisk together the mayonnaise and Nashville hot seasoning. Transfer the warm cooked pasta into a large bowl and add the mayo mixture, along with the celery, pepper, onion and sugar.
Using a large spoon, fold the chicken pasta salad together till well mixed.