You mite be right, I'm ordering a 3 incher and install the maf inside there and see if that fixes it. I also ordered new ignition coils, it also has a miss fire on idle from time to time especially when its cold. Thanks for your inputYour MAF being in a 4 inch pipe. You need to re-calibrate the values. Putting a 3 inch inside a bigger pipe will not work.
The MAF calculates the voltages according to temp of wires in the sensor. You have more air going in. So the voltages are off. Causing not enough fuel. If I remember. You could just use the MAP sensor only with a stand alone.