Mondial T check Engine Light

After a very frustrated event when purchasing the car the engine was not firing because cylinders found fouled with oil! The cause was that the engine had about 20 L of oil instead of 11 L which eventually found its way through air induction to make a mesh! Anyhow, the engine started with fresh oil in the correct quantity and new spark plugs in a thick cloud of smoke burning remaining oil for some time. After that I noticed that CEL 1-4 was ON intermittent occasionally, supposing that λ sensor was contaminated by oil and getting 1114 fault code (λ sensor). When this happens idle has an up-down behavior which is very frustrating in the traffic. I did only a few kilometers and started (always in traffic) to have momentarily ON also SLOW DOWN 1-4 with fault code 4121 (catalyzer temperature ECU) while 1114 disappeared. I suppose that this is a false alarm since I am stack in traffic but not sure. My idea is that all mesh occurred from the contamination of the exhaust system. I am on the way to replace λ sensor but in the meantime the engine is not easily firing as before and exhaust fume smelling too strong and bad. These seem to be a clear evidence that situation goes worst... Any other idea or suggestion? Any similar experience?
Thanks all in advance

 

Fortunately the gear oil level is correct.