My CL500 is having somekind of backfire. Cold starts are good but after like 10 minutes idling i start hearing a popping noise, somekind of backfire it seems but in the intake. i have the air filter assembly of and i can hear the noise coming out the maf sensor. After about 10 minutes of driving or 15 minutes idling the check engine comes on everytime and the engine starts running horrible and check engine comes on. After cooling of car starts normally. Fault codes says something about a pressure sensor, i just can't seem to find. Coils are fine, plugs are new, oil and filters changed and a new crank position sensor.

 

Anyone?