Don't spend forever trying to find your leak like I did. I ended up taking my 98 S70 to a shop for a smoke test. It took them 10 minutes to find it and fix....$50.

At 180k that's really smart. They get tired after 100k and will respond slower to changes in O2 content. The real danger is when they run the car lean and burn valves.

I went to 140k and replaced them

Replaced the timing belt yesterday. Replaced the heater core and cleaned the interior on Sunday. Today I cleaned the carpets and made a run to the u-pull it for a bunch of parts. I got an almost new overflow bottle and green cap, set of 4 floor mats, hood release, coil, 2 hub caps, 2 year old Volvo...