How to Make It
Open bottom vent of a charcoal grill completely. Light charcoal chimney starter filled with briquettes. When briquettes are covered with gray ash, pour them onto bottom grate of grill, and push to one side of grill. Adjust vents as needed to maintain an internal temperature of 450°F to 500°F.
While grill preheats, stir together oil, garlic, sugar, sambal oelek, fish sauce, chili powder, and black pepper in a small bowl. Set aside.
Thread shrimp lengthwise (from head through tail) onto 6 (12-inch) skewers (about 2 shrimp per skewer). Place skewers on unoiled grates over side of grill without coals. Grill, uncovered, 1 minute; turn skewers, and brush with sambal oelek mixture. Grill, turning and brushing skewers with mixture every 1 to 2 minutes, until shrimp are cooked through and shells are pink and crisp, about 4 minutes. Remove from grill; remove shrimp from skewers.
Divide noodles among 4 bowls. Top evenly with shrimp, cucumber slices, scallions, rau ram, lime slices, and chile slices. Serve with nuoc cham and salt-and-pepper limes.