Last week as I was driven to work my 2005 130000 miles started doing some weird things. The speedometer and the tach started fluttering and the gauge lights started dimming in tune with the fluttering. It stopped after a few minutes. Yesterday I wnet and started it and it started idling rough and when I went to drive it it started hesitating and sputtering then it cleared up and ran fine but, the check engine light came on. I took it to a local shop and they scanned it and we got a code P0300 multi-misfire. They suggested changing the plugs and running a fuel additive thru it and I did. It ran well for the rest of the day. Today I started it and it started running rough again. I took it to a different shop and they scanned it and they got the same code P0300 and a new one P0172 Bad Oxygen sensor. Could the cause the rough idle? Any other suggestions?