[blarf]

I have a 2002, 330i with 114K miles. Am I ready for new oxygen sensors?
An engine warning light comes and goes(it started around 100K miles). Performance is still OK. With new O2 sensors, would my MPG improve?

Any advice?

What code? If it's a code for the post-cat sensors, there may be not be anything wrong with them. I believe there's a TSB out for 330s regarding this... search the forums.