RPM drops and occasionally stalling.

[IntEx]

Hello.

I've got a 1 Series E81 116i 2007 [N43] manual.

Straight to the issue. Car turns on and idles normally. RPMs jump to around 900-1000 RPMs then drop after a minute or so.

So. Whenever I come to a stop and put it in neutral or have the clutch pressed down, the RPMs drop very low (sometimes the car shakes) and they usually jump right back up to a 1000. The car will sometimes stall too because of this problem.

Oil, oil / air filter recently replaced along with the battery.

I've scanned the car and I've got these codes coming up:

30E9
30EA
2AF4
2AF2
2AF6

I looked them up and from what I understood I've got a clogged catalytic converter.

I've tried putting a fuel additive thats supposed to clean the cat and the sensors too. Went on the highway for about 2 hours driving at steady speeds and the rotten egg smell went away. Scanning it again after the codes still remain.

Check engine does not light on and when checking the car through the dash control it says "CHECK OK".

So the question is. Does the clogged cat / codes that pop up have to do with the problem I've got or should I be looking for something else?