Wow....how odd is that?.....
Ok ummmm........well lemme see if I can shoot off more possible explanations....
Revo Mixing???
Is the tail servo strong enough? What're you using as a tail servo??? Not digital is it? I don't think the 190 is compatible with digitals.
Errrr, have you tried reversing the servo just for the heck of it to see if it helped? (Can you tell I'm totally out of ideas???)
Once again, all links are secure and in place? What about tail servo centering? Is it centered?
Ummm, focus on the tail servo......What type is it? Is it strong enough? Quick enough? None of it's gears are stripped??? It's not just old or burnt out???
Try just moving the tail servo without throttle and see how it does. Try all that, hopefuly something will come up!