Need Help w/ Oxygen Sensor/VANOS intake/EVAP small leak Codes on Z3

[mbhjohnson]

I recently had an engine light come on that gave the E3/E4 codes (oxygen sensor limit). Additional codes that have appeared in the past are VANOS Solenoid Intake and EVAP small leak. While everything sounds fine under the hood, I have been hearing a very high pitch 'whistling' sound that will be intermittent but is typically heard when I am accelerating. Questions: 1) Do any of these codes coincide with a particular problem that I am having with my Emission system or Fuel line? 2) Does one of these codes supersede the other and perhaps point to a main problem?

I don't want to sink a ton of money in the car but want to be assured that it is safe to drive as I am a single female. Please keep your response simple as I do not know a lot under the hood