I am having a similar problem with my V70; initially got the "Emission System needs Service" message. Local mechanic read the codes which pointed to the MAF sensor which I replaced with no change. I then took it to a shop who specialize in Volvo's and they said it was the front and rear O2 sensors which I just finished replacing, again with no change. I'm at a loss now and getting tired of throwing parts at the problem. If you have a good idea, pls help.