The rubber hose connects to the bottom of the egr back pressure transducer and then to a small diameter steal line that goes to the egr valve. The rear O2 sensor is mounted behind the catalytic converter. I would scan the codes before throwing expensive parts at it.
Here is a good web site for the villager...
http://www.loudoun-net.com/haines/vi...est.htm#cel,it has a good section for pulling your own codes without a scanner.