It looks like I mis-diagnosed and abscate is right again. This article may explain why I think I was actually chasing a bad o2 sensor. http://www.obd-codes.com/faq/fuel-trims.php Going to a different ECU simply gave me a zeroed out long term fuel trim setting which made the car stop running rough. I...

I think a clean 850 wagon is about the best looking daily driver I've had so wouldn't add anything at all. -Just my opinion. That said, were I going to do this I wouldn't use a primary color because the contrast is too great to call it an accent. In fact the more subtle the better. A lighter accent ...

I've opened quite a few over the years and all of them save for one was the brass tube type on both sides.

I concur with everything Callahan said with one exception. I would only buy a pair of spring seats and not the quick struts if mine still had good damping action. With regard to the oil cooler lines; are you going through oil? I've seen them covered with oil and road grime when they get old but not ...

I have found there is very little difference between most wagon and sedan parts and I believe the engine harness would be the same.

I would swap another ECC because it's quick and easy. It could be the problem but if nothing else would rule it out. The damper motors are hard to access. This illustration shows where they are. I found it in this thread https://www.matthewsvolvosite.com/forums/viewtopic.php?t=50525&p=251432 He ...

That sounds like crossfire to me. Cap, rotor, wires and plugs to get you to where it can be diagnosed. You may find that it went away when you do a tune up.

Start with looking for vacuum leaks.

I would load test the battery and charging system too. It sounds very much like a low voltage situation.

I always have an 850 parts car or two. Currently have a 97 850t sedan and a 95 GLT wagon.