Interesting, I was actually going to ask this very question today! I've never done a valve adjustment before, so I was curious as to how diffucult it would be to remove the rocker covers, and perform the adjustments. The biggest thing seems to be simply holding the A/C compressor up, and out of the way. I've never done this before, but I do understand the procedure from what I've read in the Service Manual, and from Volvo books as well. So we'll see how it goes! So far, I have planed to replace the alternator, rocker cover gaskets (leaks), and the muffler bracket in the back as well. So I should be able to get this done in one day, and all at once! As for my O2 Sensor, it was fried. I've not been thru the "best of times" with my motor. Everything from a disconnected Frequency Valve, to an overheated engine, to misfires that have caused my Cat to glow red. There was soot on the sensor threads when I pulled it out. But, that PRV still runs strong, and can still give other cars on the road a run for their money. But, anti-seize compound was, and always is used sparingly. No matter if it's the O2 sensor, or the sparkplugs. As for the rest of the car, all new ignition parts have been installed. I just now need to do a fluid change, and I'm set! -Robert vin 6585 "X"