Whisk the mayonnaise, Parmesan, sour cream, lemon juice, Worcestershire, garlic, 1/2 teaspoon salt and a few grinds of pepper together in a large bowl.
Add the pasta to the boiling water and cook according to the package directions. Drain and rinse under cold water to cool. Transfer to a large bowl along with the dressing.
Heat the oil in a medium skillet over medium-high heat until it shimmers. Add the shrimp, 1/4 teaspoon salt and a few grinds of pepper and cook, stirring occasionally, until the shrimp is pink and just cooked through, about 3 minutes. Transfer to a plate and set aside to cool.
Add the cooked shrimp, romaine, celery and tomatoes to the bowl and toss to combine. Season with salt and pepper. The pasta salad is best if served right away.
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