Make the pesto: Combine the olive oil, red pepper flakes, 1 clove garlic and the lemon zest in a saucepan. Cook over very low heat until the garlic is tender, 30 to 40 minutes (do not let the garlic burn). Strain the oil.
Pulse the pine nuts, basil, arugula, parmesan, remaining 3 cloves garlic and the lemon juice in a food processor until finely chopped. Add the flavored garlic oil and pulse until smooth. Season with salt and pepper.
Make the pasta salad: Bring a large pot of salted water to a boil. Add the pasta and cook as the label directs for al dente, adding the peas during the last 2 minutes of cooking. Reserve 1/4 cup cooking water, then drain and rinse under cold water to cool. Toss with the pesto, arugula, sun-dried tomatoes and reserved cooking water. Cover and refrigerate until ready to serve. Sprinkle with parmesan.