My honey ran into a Volvo guy at the parts store and mentioned to him about replacing the O2sensors and the gent told him that they had better be oem or the car might reject them and give crazy readings. Suggested we clean the old ones and put them back on the car. Is this a good idea?

Any suggestions where to start. I did the PVC system in early February . Replaced most of vacuum lines and elbows . Do you have any idea why those numbers would triple ? Did I do something wrong ? Hook something up backwards? I was on my own today . No supervision . Lol JM

Please help , before I run my beloved s70 into a brick wall.
Let me start with a little back round.
Redid the head about two years ago . The car now has 235,000 miles on it. Brand new suspension ( front end ) about 2 months old. Replaced the MAF , O2 (front and back) , new temp sensor, cap and ...