1986 2.1 van.  I recently rebuilt my engine, so naturally i spend all my free time poking around checking things out now.  I came to the O2 sensor, which is quite old and blackened. (to the point where the little slits were completely clogged).  Just playing around, i unplugged it, straped the cord to the frame, and drove it around.  The van doesn't seem to run rich.  In fact, there was absolutly no change in the performance.  That makes me think i need a new one, however, the going price I've found is $130. (i'm a poor college student).  If i shell out the 130 bucks, what kind of change will I notice in performance?  Is the 02 sensor just for emmissions, or will i see more power?  Any info is great, thanks.
Marshall Taylor

1986 2.1 vanagon transporter
1970 westy in process of electric conversion