Check the obvious, rip/torn IC boots, cracked up-pipe/y-pipe flex joint (look for soot), VGT solenoid wire chafing.
On page 5 of this link is a diagnostic procedure.
And here is the VGT relearn procedure from Bismic.
VGT relearn (from Brickie's earlier post - referencing blackhat620):
KAM (keep-alive-memory) reset & VGT learn procedure
1. Drive the truck until the engine and transmission have reached normal operating temperature.
(The VGT learn procedure requires that the oil and coolant temperatures be at normal operating temperature)
2. Flash truck back to stock (Only need to do this if running a tuner or module)
3. Turn on the headlights
4. Disconnect both batteries
5. Short out + to - battery cables to each other (Make sure both batteries are disconnected before doing this).
6. Let truck sit like this for 10-minutes
7. Turn off the headlights.
8. Re-connect batteries
9. Cycle the key to the run position twice. Pause in the “ON” position each time until the wait to start lamp goes out (minimum 5-seconds) and pause in the “OFF” position each time for 10-seconds to be sure the PCM has "gone to sleep".
10. Start the truck and let it idle for a minimum of 5-minutes at normal operating temperature. This allows the PCM to learn the EGR valve closed position value. Also you will likely hear the turbo pitch change several times during this period as the PCM learns the necessary duty cycles for accurate VGT control.
11. Complete the road test Drive Cycle:
15 miles of mixed driving (*should* be enough in most cases) to allow the PCM to "re-learn"
its adaptive strategy. Note: Anytime the batteries are disconnected, the PCM will throw the
P1000 code until the “Drive Cycle” is completed. As for the Tow/Haul mode, the transmission
must re-learn your driving style and loads hauled again as this was cleared when the truck was
Here's the VGT cleaning. Your vanes might be starting to stick.