In a large stock pot, bring water to a boil, add shrimp and cook 3 - 5 min. until shrimp turns pink. Drain well, rinse with cold water. Chill, peel, devein and set aside. Bring large pot of salted water to a boil. Add snow peas and blanch 1 -2 min. Remove with slotted spoon and run under cold water. Cook pasta according to package directions (in the same water) and drain. Rinse with cold water and drain again. In a mixing bowl, combine shrimp, snow peas, cooked pasta, onions, tomatoes and parsley tossing gently. in a seperate small bowl whisk together vinegar, oregano, basil, garlic salt & pepper. Gradullay whisk in the olive oil. Toss with pasta mixture. Cover and refrigerate at least 2 hours before serving.