98 Dodge Ram v6 error code - ideas

Been having a H**l of a time troubleshooting a problem. The error code is PO320 and I need help finding the cause.
The truck coughs while under load but at low rpm's. Dropping a gear and revving higherr clears it but it returns at the lower rpm again.
I have replaced the cap/rotor/wires and plugs but dont understandexactly what the code "Ignition/Distributor Engine Speed Input circuit is :(

Help!
added* this is a 1998 Dodge Ram 3.9 2wd....
I assume this is the crankcase position sensor but don't know where to look for this little device ????

Been having a H**l of a time troubleshooting a problem. The error code is PO320 and I need help finding the cause.
The truck coughs while under load but at low rpm's. Dropping a gear and revving higherr clears it but it returns at the lower rpm again.
I have replaced the cap/rotor/wires and plugs but dont understandexactly what the code "Ignition/Distributor Engine Speed Input circuit is :(

Help!
added* this is a 1998 Dodge Ram 3.9 2wd....
I assume this is the crankcase position sensor but don't know where to look for this little device ????

:2cents:
Take a look on the bellhousing maybe?
http://img.villagephotos.com/p/2003-12/537508/CrankshaftPositionSensor.jpg

Thanks Steve: wow I can feel it --just cant reach it. Another Dodge marvel. Anyways $175 for the sensor(260 at another dealer in town!!) and I am thinking that my local mechanic down the sreets getting this install. (40/hr)