Also own 96 Tahoe. Have they checked the fuel pressure for a possible failing fuel pump? If fuel pressure test is ok (around 60 to 65 psi) and this problem persists, I would suggest having the injectors changed out.
A lot of this problem I believe has to do with years of running a car with "dirty cheap gasoline". Cheap gas contains deposits that build up in the injectors over time and will eventually destroy them. I cannot begin to tell you how much money I have put into my tahoe over the 2 1/2 years I've owned this vehicle. I finally had to buy an OBD II code reader off the internet to stop taking it in constantly (and getting charged 40 to 60 bucks just to get a reading from the check engine light) and find out it was something as simple as an O2 sensor or Knock Sensor that is simple to replace yourself.
Another major problem with this vehicle is leaky lower intake gaskets. Watch for mysterious coolant loss and a slight odor coming from the motor with no evidence of leaking coolant on the ground. This is not an easy thing to do and a mechanic will charge about 650 to 700 to replace them. Also had the ball joints go out on mine which is not fun either. I found this out when i applied the brakes and the the front end shook like the wheels were gonna fall off. Good luck with this vehicle!!!
