So my engine idles rough, and recently my CEL came on. I'm getting three codes
P0102 - Mass or Volume Air Flow Circuit Low
P0304 - Cylinder 4 Misfire Detected
P0113 - Intake Air Temp Sensor Circuit Malfunction (High Input)
I brought it to the dealership and they swapped the coils and plugs with cylinder 2, which did not solve the problem. They also performed a leakdown which came back at 6%. They said that was "a little higher than normal".
I bought a Cobb AP and sent in a datalog for Cobb to look at. They said AF Learning 1 is adjusting fuel trim in a way that suggests I'm running rich, and that I'm underboosting. Apparently these characteristics together almost always indicate that there is a boost leak in the intake tract, and a common failure point is the pre-throttle body hose, so they recommended I replace that. I looked into AF Learning 1 and it could be doing this due to a bad or dirty MAF sensor or a bad front O2 sensor.
I get the feeling all of this is related, but I really have no experience in this area.
I've read Donkey's thread on misfires. My current plan is to replace the throttle body hose and clean the MAF. I guess I'm wondering if anything else should be done first, or what I should do after. Also, I had the code cleared, and it stayed off for roughly 1000 miles. When my car was idling for an extended period is when the code came back on.
Everything is stock.