PREPARE THE HERB AND SPICE RUB: Combine all of the ingredients in a 1/2-pint jar. Cover and shake to blend.
PREPARE THE FAJITAS: Cut the tenderloins halfway through lengthwise; pound to 1/4-inch thickness with a meat mallet. Put the meat in a baking dish; sprinkle with the rub. Drizzle on the lime juice and oil and turn to coat. Cover and set aside to marinate for 30 minutes.
Light a grill. Lightly brush the grate with oil. Grill the peppers, onions and scallions until they begin to char at the edges. Remove to a large platter and keep warm. Remove the meat from the marinade and pat dry. Grill the pork over high heat until browned and cooked through, about 4 minutes per side. Transfer the meat to a carving board and cut crosswise into thin slices. Transfer the meat to a platter, cover loosely with foil and keep warm.
Warm the tortillas on the grill until soft, 10 to 20 seconds on each side. Place them in a cloth-lined basket, cover and keep warm. Serve the fajitas and grilled vegetables with the tortillas, diced tomatoes, red onion, cilantro, sour cream and and Pico de Gallo.