Hi new member, had a long post before but had problem creating a hread so lost it..... so here it is summarised
Outback 2000 2.5L hesitates/misses under load possibly pings knocks.
Mechanic told me next thing to try was Oxygen Sensor. CEL was intermittent until after Knock Sensor Replaced (apparently throwing Knock Sensor Code)
After some research found a post suggesting PCV Valve sticking could cause this problem, took it out to clean wasn;t sticking but it doesn;t have a spring or spring broken and gone.
Could this be causing a leaning out of the mixture especially under load or should I book it in to get the Oxygen Sensor need to get the car ready for Christmas Vacation