just replaced cat and still misfiring

[v70xc]

Have you checked for dirt or possible oil leak into the distributor cap?
You might also want to check the distributor cap and rotor for areas of that are looking worn out or even cracked.

I had many misfires because of oil leaking into the distributor cap as outlined in the my previous post "1998 V70 XC AWD Random Misfire. P0300, P0302, P0304, P0305"
Maybe something in that post will help.

The following is what cleared my numerous misfire codes but only after making certain that I was no longer getting oil into the distributor cap due to a leaking Rear Cam Seal.

Zip tie the cam/crank position sensors away from the distributor coil wire. I think this might have been fixed already by the 98 models (I've never had a problem with it), but it can cause interference if they get too close.
As you can see.... jblackburn's statement above fixed my misfires. I had many codes but maybe the same simple solution could help you out depending on where your wires are running or if your Rear Cam Seal is just starting to leak a bit.

[JDS60R]

Sounds like a boost pressure sensor issue or a bad MAF or oxy sensor.
How old is the oxy and boost pressure sensor ? What do the fuel trims look like?

[Andrey]

I had a same problem on my s40 few years ago, first I replaced spark plugs to bosch, then NGK, then I replaced the coils, these didn't fix the problem. When I installed original volvo spark plugs it did fix the problem. I don't know if it has something to do with turbo or who knows. so try that before you spend a lot of money on other stuff.

[kcalia]

Thnx Volvo Spark plugs fix the problem! Runs perfect!! And i couldn't be happier! Thank you for your help!!

[Hocmiller]

Found this thread that parallels my problem and efforts exactly. I too, installed Volvo plugs and ended a long battle. Thanks for the site and thanks to the members.