Well it could be more than one issue but you would not be the first person to dump fuel injector cleaner into a ZR-1 and experience problems as a result. However the good news is that your concern about the flywheel is probably unfounded as a poor running LT5 can cause it to sound bad.
As to a Chevy dealer being able to properly diagnosis the problem, I'd say it is possible but unlikely. My guess is that you will need to replace the injectors, but before you do anything you need to have a knowledgeable person look at it. Aaron would be an excellent choice, but of course he is a decent distance away. I'd call him and see what his thoughts are.
There is a guy down in Miami that is very good, but I do not know if he has the time since he is so busy. . I can check with him for you and see what his schedule is like, so just let me know.
