[HeyKC]

Long story short: How do I know if I have a bad injector with no codes?

2014 40K on the clock. Mods included high flow drop in filters and OFT v2.0 stage 1 93 tune.
New NGK plugs and Bosch coils.

Shortest version of the long story: Went and did one of those cruises through neighborhoods for kids so this was a lot of slow stop and go traffic. (I read this is not the best on colder plugs)
On the way home I decided to get on it a little bit and the car seemed to studded but power seemed to come on fine so I didn't think too much of it at first. Car also drove home with no issues.
Skip to a couple of hours later I went to run an errand and the car was running funny. No codes and the car was actually driving fine but I could tell something was off. Pulled over in a parking lot to check it out and gave it a couple of revs then BAM! DTM error. Grabbed the scan tool from the trunk showed misfire on cyl 3. Cleared it and re-started the car. Code came right back. I was upset and confused having just replaced plugs and coils. Did a little research and saw that the slow cruising was not great on colder plugs. Ordered a new plug and put it in. Also put on one of the original coils just in case the new coil was junk. Yay! No DTM or miss fire code! Not so yay... Also the car is back to running "funny". I can start it and tell there is still a miss. I have only driven it around the block since. It drove around fine but I know its not right. Preceded to bang my head against a wall then started digging through the forums before throwing coils and plugs at it. Obviously miss fire codes usually pop up due to plugs or coils.
Do they ever come up due to an injector issue in our cars? I have read there is usually a more fuel related code. I read there is an extended warranty on these. Will BMW replace them with out a code? Can I verify it is an injector with out a code? Is there something else I should be looking at?
Thank you for any input.