Fry bacon on low until slightly crispy; remove bacon to a paper towel leaving the bacon grease in the pan. Sauté shallots and jalapeño in the bacon grease over medium heat until soft, about 2 minutes. Add blueberries, brown sugar, balsamic vinegar, mustard, garlic powder, salt, lemon juice and cooked bacon. Simmer until blueberries have split and sauce thickens slightly, about 3 minutes.
Transfer mixture to a blender or food processor; pulse until pureed. Return sauce to pan so you can warm it slightly when the meat comes out of the oven.
For the pork, remove the silver skin, if any, from the pork tenderloin. Season the meat generously with salt and freshly ground pepper.
Preheat grill to medium high heat (375° F/ 190° C). Place meat thermometer in the thickest part of the tenderloin. Cook, rotating sides, for 20 to 25 minutes, or until thermometer reads 145° F (62° C).
During the last 5 minutes of cooking, brush a little of the sauce on the tops of the tenderloins, just enough to adhere to the meat.
Remove tenderloin from the grill and loosely tent with foil. Let sit at least 5 minutes before cutting on a diagonal into 1⁄2 inch- (1 cm-) thick pieces and serve with remaining sauce on the side.