[shirkenikhil@gmail.com]

I've been encountering a concerning issue with my 2017 BMW 320D GT's engine performance. When I'm not accelerating, the engine rattles heavily, but at higher RPMs, it seems to run smoothly. Additionally, I've noticed lower mileage than usual.

Upon running diagnostics, I received the following error codes:

- 2A6D00 Permanent Smooth running Regulator Cylinder 4: Correction Quantity outside permitted Limit
- 2A6D00 Permanent Smooth running Regulator Cylinder 1: Correction Quantity outside permitted Limit

Here's what I've tried so far:
- Replaced fuel injector No. 4 with a new one at Cylinder 4, but the error code persists.
- Replaced injector 1 with a new one, yet the error code remains.
- Cleaned the EGR system, but unfortunately, the error code persists.
- Ensured there are no air leaks.

Even after resetting the diagnostics tools, the error codes persist, and the engine's performance suffers when not accelerating.

I'd greatly appreciate any insights or suggestions on what could be causing these issues and how to resolve them, also any reputable mechanics who can solve this in Harrow, London.

Thank you in advance for your help!