I just fixed this exact issue on my early build 98 V70. I had the P0455 code, but not the P0440. I could reset the code and it would come back.

I think the 850's should have the vapor canister with the "J" hoses in front of the left front wheel. Later models put the canister next to the fuel tank in the rear. Check those "J" hosess for sure.

Also check the small length rubber hoses on either side of the rollover valve - which on my car was located next to the fuel filter in front of the right rear wheel. Its probably covered with undercoating and grime. The small length rubber hoses transition between the plastic hard line and the rollover valve. Both of mine were in very bad shape.

Klaus is right about the smoke test being the best way to track these type of leaks. I was too cheap to have one done, so I would up dropping the vapor canister, the gas tank and tracing all the lines to evenually find my problem. It's more work than I should have done, but I now have a pretty good understanding of the EVAP system on the car!

Best of luck on both the repair and getting your life back together!