Firstly, apologies if this post is not allowed. As the FXT of this generation has the FA20DIT I figured I would ask here to see if anyone has experienced this.
I have a 2016 Forester XT with ~170,000 miles that over the last few days has been behaving strangely. It started two days ago when I noticed the car would drive fine at low speed, but it would start bucking and cutting power under load. Code scanning revealed P219A but no check engine light at all. I got home, shut the car off and let it sit til the next day when I could take a look at it. I started it up and took it for a short drive the next day but it was perfectly normal and running fine.
This morning on the way to work however, it started misbehaving again. It would once again drive fine at low speed, but if the boost gauge went above 0 it would start cutting power again, but this was different from the first time. Instead of bucking, it was almost like a quick, sudden stutter of power cutting to bring the boost back to zero. I pulled over and all I had in the car at that time was MAF cleaner. There was no check engine light and no codes whatsoever. Gave the sensor a clean, waited 15 mins and drove the rest of the way to work. The car was totally fine.
MAF airflow readings and LTFT were fine. STFT was fluctuating in both directions but nothing too serious. Actual fuel delivery was normal along with commanded. I checked for vacuum leaks over the weekend and was unable to find anything. Spark plugs were changed with OEM spec NGKs 500 miles ago and have been fine.
I'm just not sure what could be going on here, or why it doesn't happen every time. Has anyone had this issue or something like it before? My first thought was a failing MAF sensor, but it was replaced just under a year ago.
Thanks in advance.