Hello Everyone:
I changed job last year (after more than 180 days) and informed USCIS about it by sending the following documents:
1. A letter stating that I haved changed job well after 180 days. Also, mentioned that it is a similar position and provided the date of joining.
2. A letter from my current employer mentioning the job description (same as labor), date of joining, salary and position (was different than the one in labor)
3. Copy of my I-485 receipt.
In february this year, I got an employment RFE from USCIS. I replied by sending:
1. A letter from my current employer (same as the one I sent during AC21)
2. A cover letter mentioning that I informed about using AC21 last year.
Just this week, my I-485 got approved.
I hope this helps. If you guys have any questions related to my case then please let me know.
Good luck!!!