i know its a little off topic and a little smaller than an a340 but on en emb 120 on the r/h wing root faring there is a "vortice generator" (i use the term lightly). Its whole purpose in life is to reduce vibration on the vertical and horiz stabs, was making pax in the back sick, fit one of these and the pax stopped getting sick. Could it be something similar? (just asking)