Prepare a grill for indirect heat: If using a gas grill, turn all the burners on high, close the lid and heat until the internal temperature is 400 degrees. For a two-zone grill, turn off one side. For a three-zone grill, turn off the center zone. If using a charcoal grill, remove the top grill rack and light the charcoal; when the charcoal is covered with ash, mound on one side of the grill. Return the top rack.
Cut out eight 8-by-12-inch pieces of heavy-duty foil. Layer to make four 2-layer stacks. Fold up the edges and corners of each stack to form four 5-by-8-inch boats. Spray with cooking spray.
In a large bowl, whisk the eggs. Fold in the chips to coat. Place the foil boats on the lit side of the grill and heat 30 seconds. Divide the egg mixture among the boats and add 1 tbsp. salsa to each. Cook, stirring occasionally with a heatproof rubber spatula, until the eggs begin to set, about 1 minute. Slide the packets to the unlit side of the grill and cook, stirring occasionally, until the eggs are very softly set, 3 to 5 minutes longer. Top with the cheese, cover and cook until the eggs are softly set and the cheese is melted, about 1 minute. Transfer the packets to plates and top with the avocado, cilantro, hot sauce and onion.