Combine soy sauce, bourbon, and brown sugar in a shallow dish or zip-top freezer bag; add tenderloins. Cover or seal, and let stand 30 minutes at room temperature, or, if desired, chill 8 hours.
Remove pork from marinade, discarding marinade.
Grill, covered with grill lid, over medium-high heat (350° to 400°) 12 minutes on each side or until a meat thermometer inserted into thickest portion registers 155°. Let stand 10 minutes before slicing.
Stir together sour cream and next 4 ingredients; serve with pork.
Note: Pork tenderloins may be baked at 500° for 20 to 25 minutes, if desired, instead of grilled.