Failing alternator will throw a bunch of odd CEL DTC codes. Some your other symptoms match those associated with a bad alternator. Get it checked.
Thanks, I had it checked last night, it's all good. The battery is 2 months old, and after the grounding mods, and resetting the ECU, the check engine light didn't come on... until this morning on my way to work.
I'm going to connect my laptop this evening to find out what tripped the CEL.
The downstream O2 sensor was replaced a couple of months ago. I have the upstream Air/Fuel sensor waiting to go in, although I've never received a CEL code that it's bad. I believe it was replaced before.
Now to add even more to the hateful nature of this beast.
Without the CEL on this morning, it was still bogging and stumbling.
As soon as the CEL came on, the bogging and stumbling quit. So, I'm leaning away from the fuel pump/o-ring problem. Again, I haven't had a chance to connect my laptop and pull the code for the CEL, but this makes me think it's a failed sensor. I'll know more later this evening.
I inherited this car from my mother who bought a 2011 Outback, because this one was having so many problems. The dealership offered her $500 for it on trade in, with an identical 2001 sitting on their lot for $8990. She understandably balked, then sent the car to me.
I'm a BMW guy. I have four BMWs, and never really wanted a Subaru but it is really a nice, handy car, provided I can get all the problems lined out. It drives well, and when it works right I'm actually impressed by the power of the 2.5, it's not gonna win any drag races, but that's not really it's purpose. One of my BMWs (a '96 Convertible 328i) had very similar drivability issues and it turned out to be a camshaft position sensor.
Thanks for all the suggestions, and I'll get more information this evening.
P0442 Evap System (Small Leak) was the reason for the CEL.
This morning on the way to work, it was really bad. I think I'm just going to start throwing sensors at it, until I find the one that fixes it. I'm starting to think it's some kind of timing issue. It'll be fine sitting at a stop light, press the throttle and it takes off well for 100 feet then bogs/looses power. Floor the throttle, and at around 3500RPM it comes back to life like it has no issues.
On the interstate, cruising at 70MPH, it's almost impossible to maintain speed, because it feels like the power just goes away, comes back, and disappears again. When it starts this, I can kick it into passing gear, and the problem disappears above 3500 RPM.