I agree with these posts.

In my case I live in Thailand where the average bus puts out a smoke screen for a kilometer. My dealer (not a Volvo dealership) removed the cat and put in a bypass instead of spending money on a replacement under warranty. You guys don't know how lucky you are out there in civilisation !

Anyway - this is what I found. Helluva noise inside the car, similar to a trumpet player inside a large cave - for me, impossible to drive a car sounding like this. Might be OK for some immature teenager who likes advertising the fact though.

I had access to a friendly muffler dealer locally and played about with the exhaust systems he sold.

Adding almost ANY muffler (turbo style or straight through) at the rear of the car brings the noise almost down to stock, adding another small straight through muffler where the CAT used to be brings it back to stock levels. Adding the inevitable chrome piece of junk on the end (Thais love these - the bigger and shinier the better) does nothing at all, of course, except deplete your wallet. I practically had to fight them to take it off !

I left in the original Volvo pan muffler - I thought I would try to keep some back pressure on the engine/ turbo as the ECU is not modified and I don't want it to run rich. However, it did not appear to be particularly restrictive to us.

Power - after CAT removal bottom end power much the same, top end seems a little improved. However, I can't see any real difference after the addition of the mufflers.

FYI my car is only fitted with one O2 sensor which makes it a lot easier for me.

KP