Air filter is new, turbo looks and feels okay with "elephant trunk" off. Sounds like next step is to pull injectors.Have you checked the air filter by chance? Also sounds like you may have a bad O-ring (s) on the fuel side of an injector(s). Also, pull the intake piping off to the inducer side of the turbo. You may have an impeller that is in bad shape.
Its a long shot but someone may have installed a single shot injector or two in it. That would give it a rough idle too. But this is not very common but can happen.
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Its probably going to have the AD injectors but not for absolute sure until you pull the valve cover. Being its a 450 it may have single shots but I doubt it.Ran a buzz test twice, first time 2 and 8 failed, 1272 1278 1293 1294 passed the 2nd time. On the CCT Cylinder 2 failed. Which injectors does this motor have?