is activating for some reason when in 5th. If the cable moves smoothly at rest it should work the same in any gear unless the cable binds due to loose motor mounts. I would not think that would be the case in 5th. Are you sure it actually sticks. There are other reasons why it might idle high. If the IACV was sticking or shorted it could feed extra air bypassing the throttle plates. If you have Nissan Data Scan or similar with a cable, you could verify the TPS switch closes when letting up on the pedal.