2001 Yukon Loses Power When Hot

I have a 2001 Yukon that loses power when it is extremely hot, often after sitting at idle for an extended period. We cross the border between Saudi Arabia and Bahrain and sit in queues for long periods of time in hot weather. After the last station, when accelerating back to highway speed, the engine makes a whining noise and doesn’t have much power. After operating at speed for a short while, the whining usually goes away and operation returns to normal. I have heard that this might be the alternator or torque converter. Any ideas.

For the weak acceleration, change the fuel filter. To check fuel pressure, attach fuel pressure gauge, and run engine in Drive, for two to three minuets.
Alternators can whine. Power steering pumps whine louder. Check the level of the power steering fluid. Check the voltage and amperage output of the alternator.