Engine Chugging up a hill

I have a 99 Tahoe with 60K miles. When I am on the interstate going 70 mph and start to climb a hill the tranny downshifts and then the motor revs. The RPM's stay up for maybe 15 seconds and then the motor starts to chug and mis. Speed declines and the truck vibrates. I let off the gas and it takes around 10 seconds for the motor to straighten out. It runs fine until the next hill, and then it happens again. I have had it into the dealer numerous times and they can't tell me what the problem is. I have tried fuel system cleanings, new plugs, air filter, fuel filter, etc. I have had the problem since 45K. The next thing the dealer suggested is new injectors. I'm not sure I want to spend that kind of money on this vehicle.

Any suggestions would be greatly appreciated.

You don't need new injectors. If anything you can have your current ones reconditioed for about $15-$25 each. Here are 2 links you can look @.
http://www.cruzinperformance.com/fuelinj.html
http://www.fuelinjection.com/
Hope this helps. If you do take them out and have them done, make sure you label each one and put it back in the same exact spot as before.
Also, I think it is very possible that your torque converter is going bad. Have a tranny shop check it out. I don't think you need a new tranny but have them check it and get a couple differnt shops to look @ it.

Hope this helps.