I read an article about how road salt can be a factor in having problems with the brakes on your 99 Tahoe.  If you check out this web site you will see what I am referring to, in the “GM Recalls Cars in 14 States, story.  I don’t know where you live, but I wonder if this could be part of your problem.  http://www.redorbit.com/news/business/252185/gm_recalls_cars_in_14_states_for_brake_problems_but/. Also, the people at this web site let you ask your brake questions, and they will tell you the answer. http://appliance.justanswer.com/JA/ASP_ASK/FID_14/K_196/P_0/TR/Used-Press-Brakes.htm.  I hope this helps you with the brake problems you are having.  I also read on several other web sites that the Tahoe’s from 1996-99 had to have the brakes repaired and rotors replaced after only a few thousand miles; so I wonder if there is a defect here, and if the dealership should have sent you a letter about having the brakes checked, or repaired at their expense.  It certainly is worth looking into.