Passat not working right

To make sure I get the story right, a few questions;

The car was running ok, then had a symptom which led to taking it to a repair shop where the injector was replaced. What was the symptom that led to the repair?

Were you told that only 1 injector failed and that replacement oiwuld take care of the issue?
Were there any other items replaced, spark plugs, etc?
My first thought is that the incorrect injector is installed or the computer is having problems reading it and re-setting it might help. Or, there is another issue that might have to do with the original problem that still exists and is getting worse.
Let me know and I will respond ASAP and help you out.