1. Toss potatoes and 2 tablespoons oil in large bowl. Cover tightly with plastic wrap and microwave until edges of potatoes are translucent, 4 to 7 minutes. Halfway through microwaving, shake bowl (without removing plastic), tossing potatoes to ensure even cooking. Meanwhile, combine vinegar, garlic, 1 teaspoon sugar and 1/4 teaspoon pepper in large bowl. Slowly whisk in remaining oil until emulsified. Stir in roasted peppers, capers and parsley.
2. Pat pork dry with paper towels and season with 1 teaspoon salt, 1/2 teaspoon pepper and remaining sugar. Grill over hot fire until browned on all sides and meat registers 145 F, about 12 minutes. Grill potatoes until charred and tender, about 5 minutes per side. Transfer pork to cutting board and tent with foil. Toss grilled potatoes with dressing to coat. Season with salt and pepper. Slice pork and serve with potato salad.