So my brothers Q50 has been pulling these codes for a while now and originally we had taken it to infinity to have it diagnosed and they said that it was leaking fuel injectors so we had replaced them and after the car ran fine for around 400 miles and then started pulling the codes again so we had tried just cleaning the maf sensors which seems to make it run good for about a half an hour before the idle starts to fall again and the a/f ratio leans out so then we had tried replacing the intake manifold gasket since it was recommended when we did the injectors and we didn’t do it then however that didn’t seem to help either I also don’t think it’s a problem with the fuel system because we’ve never had any issues on startup. And so I was just wondering if anyone has had a similar situation or has any advice before we just continue to throw money at it

Ps the codes are that both cylinder banks are running lean. And we had also replaced the maf sensors