Make a good charcoal fire in grill. When coals are almost gray, spread to make even layer. Set tomatoes and chiles on lightly greased grill 4-6" above coals. Cook, turning as needed, until chiles are charred on all sided and tomatoes are hot and streaked with brown. Add small amount new charcoal, and mound for indirect heat. To make salsa, chop grilled tomatoes and chiles; discard stems and seeds. Place tomatoes and chiles and their juices in a bowl. Stir in vinegar, cilantro, and garlic; season to taste with salt. Spread some of the salsa evenly over both sides of ribs. Place ribs, meat side up, on grill directly above drip pan (overlap ribs to fit on grill if necessary). Cover varbecue and adjust dampers as necessary to maintain an even heat. Cook, bastin occasionally with some of the remaining salsa, until meat near bone is no longer pink; cut to test (1-1 1/2 hrs.) To serve, cut ribs into 2 to 3 rib portions; garnish with lime slices , if desired. Pass remaining salsa, sour cream, and lime wedges at table. To eat, top ribs with salsa, sour cream, and a squeeze of lime.