i just picked up a euro 635 1981, it runs real rough and smells gassy in the exhaust, i saw that the o2 sensor is not hooked up where does it go, the wire that is where does it connect to,, also on the computer it looks like there are two sets of grey wires that were added to the harness, one is connected and one isn't what are they fore(if you disconnect the one connected the car wont start. thanks dave