Vortilons: In an old DC-9 new hire aerodynamics book from my present employer it is stated that vortilons were added to both lower wings inhibit spanwise flow on outboard wing sections at high angle of attack. This preserves lift on outboard wing sections and insures a positive nose-down pitching at higher angles attack.
It appears that vortilons have been used to avoid T-Tail deep stall. This was similar to what I was told by Flight Safety when I asked about them in Falcon-20 initial ground school.
Hope this helps.