E91 320i with high emissions

My 320i from 2009 with N43 with 160 000 km has failed the yearly vehicle check in Sweden for the emissions at 2500 rpm.

Values as below:
Idle: CO 0,1(0,3 allowed) HC 008 (100 allowed)
2500 rpm: CO 2,1 (0,2 allowed) Lambda 0,94 (0,97-1,03 allowed)

The car was checked by BMW and NOX-sensor and a low pressure fuel sensor had failure code and was replaced. It made some change since stop/start function started working for the first time since I bought it 70 000 km ago. (Was told that the loss of stop/start probably was caused by bad battery or similar reason).

However, the emissions was not improved and the garage told me that probably the cat converter had been damaged by driving with faulty NOX-sensor so the cat was changed last Friday.
This did not either give any improvement...


There was however a new failure code registred which had something to do with one of the cams. There is also a rattling noise from the engine when it is cold in the morning, easiest heard at approx 2000 rpm. I suspect this is the beginning of the timing chain issue and the BMW garage wants as the next step to reset the engine to see if this is the reason by resetting the engine.

Can a bad timing chain really cause the high emissions?
Or does anyone else has any clue for the emission issue?

The car has all the services done at BMW and there are no campains to be done on the car by BMW. Last service was done late last year.