I have a 2005 V70R with 117K on it. I bought it new at Boston Volvo but I am ready to give up on them. they are trying to sell me a $4K valve job. Check engine light went on and that led them to do a leak down test. Compression was low on 2 and 3 but BV says they fixed it by "decarbonizing" Still running very rough at low speeds( 2000-3000RPM). Brought the car to Peabody Auto clinic and they can't give me an answer on whether to keep or trade. they say it needs a new mass air sensor at $400 and that MIGHT fix the problem but no promises. I have always run premium and used Mobil 1 but I don't know if engine is toast or if it is easily fixed. I am willing to put another $2k into the car if I can get to 150K miles.<p>Any ideas or opinions? I can get $12K now for it in trade; will that go to zero if I keep driving it without any work?