2002 Chevy Tahoe stalling at high speeds /and acceleration

Plse help the dealers are nickle and diming me to death. About 2 months ago our tahoe would stall going down the highway. The wife would pull to side and restart. I would throw it neutral and do it when it happened to me and this was now and then. Lately since she is the regular driver happening more often, it been to several dealers they cant dupicate problem. Seems when 2 hours into a drive it starts acting when accelerate. As of last week the wife went to richmond va a 4 hour drive that took her 6 hours to get there kept stalling and taking longer to cool down or reset it self. Later that evening the wife and her sister left for outer banks a 3 hour trip and it did it to her again. I had her take to chev dealer next day in kitty hawk $750 dollars later were sure problem solved they say! Change fuel filter checked fuel pressure checked senors (heat and o2) tune up changed oil checked injectors all good to go. Victory cheverolet sure problem solved. She gets car notices a little hesatation but not sure she lets it go. Start trip home 2 hours into it it dies and then the whole routine starts over. She scared she gonna get nailed in the backend or shut off in a tunnel or on a bridge.
customer service cant help due to age of vehicle. When she got closer to home 7 hours later it was shutting off every 10 miles thus pull over wait till can start. Quick trip around house are fine she is out in it today no problems plse help cant afford new 1 and
service depts say lets change this, lets put this in etc signed at wits end norm