Engine rev high gear won't switch easy
You should have the vehicle scanned for codes. I suspect the Throttle Positioning Sensor.
YES, TPS is a common problem with the I6 engine. Need to replace whole throttle body as the TPS isn't removeable from it.
If this is a 5.3L engine then you can replace the TPS, but on the 4.2L engine you can not. The throttle body would need replacing as FJ4072 says.
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