The mechanic who sold me the car replaced the O2 sensor. Shortly thereafter the LS light returned. I reset by removing the neg. battery connector. Drove about 100 miles and it came back on. I noticed that it usually comes on after driving on the highway...after I stop and resume travel. I guess that when you stop, vacuum should be at max. Last night I found the small hose on the flame trap highly deteriorated. It was broken in 3 places across half it's circumference. I replaced it and have not yet used the car. As I told you in my previous post, the plugs are not Volvo but aftermarket Bosch, single ground prong.(Car is non turbo) I have Volvo plugs but did not install them because I want to see if it was the broken hose. I could not find the sensor under the thermostat housing but it started to rain heavily so I clocked out 'till later. I'll keep you posted and thank you for all the help.