posted problem/soultion other threads, may help
Hello!
We had the "Elvis" hesitation when going up or coming down slight hills - "uh huh, uh huh, uh" as car was trying to shift to different gear or plain hestiatating
Subaru check transmission and all the other things to the wheels. Nothing. The sensors seemed OK, but husnband convinced it was a bad sensor someplace.
Then he noticed the tube from the air thing feeding the motor that was connected to the "pcv" was not a continuous rubber tube. it was splced, with no clamps on either end, and it was really loose. Probably leaky.
He put hose clamps on each end and VOILA! Smooth as the day we bought it.
He got the idea from his old truck, which had a bad "pcv" thing.
No that I think about it, I wonder if Subaru replaced the thing after the last check up?
J. sends