My wife sometimes runs on nearly empty. Then we had a noticeable drop in car performance.. having to go up hills in 1 or 2. Noticed the red light was on and we had an engine system warning. Thought it might be the dpf and after checking oil and water I decided to raise the pressure on the sytem to get rid of any clogging in the dpf. I accomplished this when stationery and I could rev the engine as much as I wanted. A cloud of smoke came out. But still the problem persisted of lack of power when driving up hills. I replaced the air filter and cleaned out the egr valve. I noticed one of my sensor plugs which mixes the air ratio was full of oil which must have drained down the sensor. I have dried it out and cleaned out the air tubes using a cotton bud to remove dirt. I also cleaned the Maf sensor. Over a period of time previously there has been some oil which has been getting sucked out of the oil breathing tube towards the turbo. I regularly clean this out and the turbo feels solid. However some oil has come in there. Did a scan on engine code P0001 coming up. I feel a bit stuck and in doldrums at the moment. Very greatful for any advice

Richard