Bring a large pot of salted water to a boil. Add macaroni and cook until very soft — slightly more tender than al dente, about 10 to 12 minutes. Drain, rinse with cold water, and let cool completely.
In a large mixing bowl, whisk together the mayonnaise, vinegar, sugar, mustard, salt, and pepper.
Stir in the grated carrot, celery, pickle relish, and minced onion until evenly combined.
Add the cooled macaroni to the bowl and gently fold until the pasta is evenly coated with the dressing and veggies.
Cover and refrigerate for at least 2 hours (overnight is even better) to let the flavors develop. Stir before serving and adjust seasoning if needed.
Notes
Cook the pasta until soft, not al dente, for the most authentic KFC texture.
Rinse pasta under cold water to stop the cooking and prevent clumping.
Finely chop veggies so they blend evenly into the salad without overpowering bites.
Chill for at least 2 hours before serving—overnight is best for maximum flavor.
If the salad thickens in the fridge, stir in a little extra mayonnaise before serving.