So I replaced plugs, rotor, distrib., filter, cat, both 02 sensors, changed oil, cleaned up under hood, and th ecar is running better than ever, a few squeeks here and there still, belt needs adjust...just did a hole shot in my driveway...yay! Now the question is- do I sell the 855 or my 03' passat, I cannot keep both, and money wise I think the passat will hold its value better than the 850? any thoughts.

Cats don't die, they are murdered by rich mixtures.

1. Get the engine running properly, remove/punch-out the cat if necessary

2. Drive the car and make sure the problem is fixed before you replace the cat.

3. If you need to pass an emmissions test take the car for testing with no cat, in proper tune it could easily pass that way.

4. Any three wire (heated) O2 sensor is interchangeable, I would pay the money and buy the sensor that plugs into your car without any re-wiring. You risk poor connections, incorrect wiring, and other issues by trying to save a few bucks here. Yes you can do it, that doesn't mean it's a good idea for a do-it-yourselfer.

5. Consider cleaning your O2 sensor, and then checking the output voltage, it could be fine.

6. Get to the root cause before you start throwing money at the problem.

Slow down... What makes you so sure the cat has failed? The car idles but you can't give it gas above 2000 rpm without flooding out? Or is it just the error message that cat may be damaged due to misfire?
First, change the plugs, wires, and rotor/cap. Get Volvo plugs, they are really good for 40K miles and put anti-sieze on the threads.
Then check the injectors if the misfire continues, by unplugging the electrics one at a time and listening to the idle. Get them cleaned if the idle does not change.
Find another mechanic.

Klaus
--
Please answer, we need to know if the advice is good or bad. The 164 has a new home, all I am left with are 2 turbos :)