So the rear O2 sensor went and I changed it and reset the ECU. I had also changed the Coolant Temp Sensor because it wasn't starting properly (it would start but die out without giving it a quick rev). But now the idle is at about 500 and dips in neutral to about 400 and then back up and the temp guage needle moves up and down (like a jerky motion over bumps or if i tap on the dash near the guage). Any suggestions?

 

There are 2 engine coolant temp sensors. The gauge uses a different coolant temp sensor then the ECU. Did you replace the correct temp sensor? The fact that a tap on the dash makes the gauge move around tells me you have an issue on the instrument gauge pannel.

Clean your throttle body to help correct your idle issue.