In a food processor, combine the pine nuts and garlic and process until finely chopped. Add the 3 cups arugula and process until coarsely chopped. With the processor running, gradually add the olive oil in a steady stream and process until smooth. Turn off the machine and add the lemon juice and cheese, then pulse until incorporated. Transfer the pesto to a bowl and season with salt and pepper as needed.
Cook the pasta until al dente. Drain and set aside.
Toss the shrimp with the oil, garlic powder as well as salt and pepper. Saute for about 3 minutes on each side until pink and fully cooked.
In a large bowl, toss the pesto with the pasta until well coated. Scatter arugula leaves on top and sprinkle with extra cheese. Serve immediately. Serves 4 to 6.