P2279 Air Intake System Leak - C220 CDI

[11esprit]

I am having an intermittent issue with my 14 C220 Cdi 170. The car sometimes runs rich and also lumpy going up steep hills and shows a code P2279 but the code doesn't store and only shows pending. I have had the vehicle smoke tested for any leaks but no leaks are showing. Are there any other areas I can investigate I am thinking MAF Sensor, EGR, Oxygen Sensors or leaks in the intercooler or the hosing. Any replies are appreciated.