Code P1216

[Stratosurfer]

Suburban is throwing P1216 and mech changed out throttle sensor, FSD, ECU, verified lift pump working. He changed out everything except the injector pump and the Optical Sensor with the Tahoe to troubleshoot.
Symptoms are: throttle pedal overly sensitive and engine will stall around 2000 plus rpms but will not die.
Mech says he changed out everything except the Optical Sensor and the injector pump and doesn't want to do an injector pump if this is not the issue, I agree obviously.
Any ideas, can this be an Optical Sensor?
Help needed, thanks in advance.

[Stratosurfer]

All,
My mech and Mr GovtWrench said it was IP. Bought rebuilt from Pensacola Diesel Injection, $450 (w/o PMD) included shipping, mech put on for $275 and spinning like a top. Mr. Govtwrench wanted $1150 for a new pump and $675 labor to install...
I do recommend Pensacola Diesel Injection as a rebuilder. BTW they required no core.

[6.5 Detroit Diesel]

$450 isn't bad for an IP, eh? glad to hear you got it all back. three years ago we needed a DS4. local dealer wanted $1500 for parts alone. there has got to be some incredibly stupid people out there for stealership garages to stay busy.