AFAIK, the challenge with these shocks is that one of the end mounting holes is not set at exactly 90 degrees to the piston rod. That means that another shock of the correct length, etc. doesn't fit and work.

Could be lots of things. Possibly a vacuum leak causing lean running on 4 and 5? Bad intake manifold or manifold gasket? That is but one of many possibilities.

row52.com might help you find a comparable donor vehicle in a local wrecking yard. A lot of 960s and V90s are heading to the bone-yards these days.

I realize this is a strange problem to have. Background: Over a year ago I took apart our 1998 V90 to replace the heater core. Those who know realize this is a nasty job which requires tearing apart a goodly part of the dash and interior. This is an extra car for us and life got busy, so there was a...