A few things I would be thinking about would be fuel pressure, high pressure oil leaks, boost leaks, and harness issues.
You said you had a shop do a buzz test, why don't they just diagnose it?
Can you monitor PIDs? What is your ICP reading at WOT? How much boost can you achieve?
The code P1316 indicates you have injector circuit problems. Did you perform the test that Brendan recommended?
Jay