I have been going back and forth between this forum and an Australian forum.
You have 2 cylinder misfires, EVAP issue, low idle. Fuel filter has been in more than a year and how many miles? You don't know when the plugs were replaced last.
97 Impreza with a 2.2 is run by a MAF and uses a MAP/BARO to calculate atmosphere and vacuum changes.
Vacuum leak could be the cause for the misfires and EVAP, but then at the same time you have a low idle which could be caused by a TPS data issue due to carbon build up or poor fuel delivery which could also cause misfires which effect vacuum in turn screwing with the EVAP.
Are you following me here?
One, if I had caught earlier that two post on the same car at the same time with connecting issues, this could have gone easier. So in the future, put it all in one post.
Two, it is apparent there is a maintenance issue, as in lack of maintenance.
So, lets start over.
Check the battery cables and grounds.
Change the fuel filter.
Get a set of NGK or Denso plugs and replace the ones you have. Get a set of Packard or NGK wires while your at it.
Clean the throttle body.
Make sure there aren't any cracks in the intake tube between the MAF and the throttle body.
Check for vacuum leaks anyway.
You may as well change the thermostat and flush the coolant out to forestall that thread you post about a P0420.
When you have this done, calculate a time for flushing all the other fluids on the car: trans, diffs, brake and power steering.
Clear the codes. Drive it. Then let us know how the car is running.
Update: changed spark plugs, spark plug wires, two fuel lines, fuel filter, and one vacuum line, check engine light is off for now, idling smooth but still around 500 rpm. Is it normal for the 97 Impreza OBS to idle that low?