Hey guys, could really use a bump on this thread. Ive got 4 o2 sensor codes showing lean upstream and downstream as well as a code for connection to pcm. Car has been stumbling at times for months before the codes showed up. Also, having intermittent random misfire codes. Could use some advice....is this a bad o2 sensor leaning out banks1 & 2, not communicating with the computer, or good sensors indicating vacuum leak or perhaps poor fuel delivery. Which of the two scenarios is more likely to accompany random misfire? Thanks in advance.