They tried to get me to wait 3 to 4 weeks for a "GM Rep" to come in and go for a ride with me. I said no, I've already ridden with the mechanic and service manager and both know how it felt. They had my truck for a week that time and they had already balanced the tires twice before. I insisted that something be done. Since they had run all of the pico-scope analysis and sent the data to GM techs and the techs said it was all within spec they got agreement from GM to replace the tires. Have they done the pico-analysis on your Tahoe? If not, you might want to get that done before the engineer get's there.