Drizzle the banana peppers and the jalapeno with vegetable oil and season with salt. Place on the grill over direct heat; grill on all sides, about 2 minutes per side. Set aside to cool before removing the stems and seeds.
Combine the cider vinegar, mustard, brown sugar and 3 ounces water in a medium pot over medium heat and bring to a simmer.
Meanwhile, add the grilled banana peppers and the jalapeno to a food processor; pulse until smooth. Add the pureed peppers to the simmering vinegar mixture, stirring until combined. Slowly whisk in the flour, taking care not to create clumps. Lower the heat and simmer until the sauce reduces by one-quarter to an apple-butter consistency, about 20 minutes. Remove from the heat. Set aside 3/4 cup for glazing the pork; the remainder to be used for serving.
Drizzle the pork tenderloin with vegetable oil and sprinkle heavily with salt and pepper on all sides. Grill over direct heat for 1 to 2 minutes per side. Brush with 2 tablespoons of the banana pepper compote and move to indirect heat. Cook until an internal temperature of 140 degrees F is reached, rotating the pork 45 degrees every 5 minutes, and brushing it with 2 tablespoons of the compote after each rotation, 35 to 45 minutes total.
Remove the pork to a cutting board. Let rest for 10 minutes before slicing. Serve with remaining compote.