MY01/02 WRX?

WRX variants have what we call TGV valves, i've seen a few of them which have misbehaving TGV's sensors and actuators before. Sometimes the valves shut due to gum buildup or just actuator fault and thus produce all kinds of issues.

Do you regularly use upper engine cleaner?

Thought about removing them?

Personally, i've only ever had a problem with a brant module on a MY01 WRX back in the day. Car would perform faultlessly and then randomly jerk around and cut out. This was resolved by having Technik Car Audio (Macey) install an aftermarket alarm and audio gear (and yes i even had doof doof back in the day).