Checking on Rockauto.com for injectors I read this for the AC Delco spider injector:

What are symptoms of a problematic injector?
Check Engine Light/Misfiring engine caused by a change in the injector's flow
Noticeable fuel odor caused by leaky injector
Reduced gas mileage caused by an incorrect injector spray pattern
Inconsistent engine idling, hesitation or stalling caused by dirty injectors due to low quality fuel

This is exactly the symptoms I have, the whole list is what I have when it happens.