The MAF tells the ECM how much air is going into the engine and then adjusts fuel accordingly. Wrong input to the ECM means your truck won't run very well. About 38 at idle is correct, 27 is too low, no information about what it should be at WOT. It could be a problem with the sensor itself or the circuit. They are reasonably expensive so I wouldn't replace it unless you are true that's the problem. I have attached some info about my 2008 model so that you can test the power and ground for the sensor. Pin 3 is the input of battery voltage and pin 2 is the low reference (ground). The signal goes out to the ECM on pin 1. Are you using an OEM sensor? Is there any particular situation where it shows the problem more than others?

 

The sensor is brand new oem from MA. It also reads exactly the same as my old one. So from my understanding of the wiring diagram, pin 1 is the 5v ref for Maf. Does that mean with key on and maf disconnected I should be reading 5v from that pin?

 

Pin 1 is the response to the inputs to the sensor. I have been told by some who measured it that it was indeed 5V. If you have the correct battery voltage and low reference, your MAF should produce the correct reading on pin 1. See attachment re testing the MAF.

 

Thank you so much for this info. I will test the maf wires and report my findings.

 

The air filter is clean and free of any obstruction, correct? If so, with everything else you've listed, I think you're on the right track.