From those voltages, it seems to me that the downstream O2 is the problem. Have you tried running with it disconnected? There should be a connector somewhere up there so you can just unplug it.
If you can get it running evenly, I'd like to know what the voltage is across the battery with the engine idling. Anything more than 14.9v is bad, and you will need a new alternator.
Also, you say that the TPS is at 18%, do you mean that it is reading 18% at idle/rest?
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Originally Posted by the user formerly known as ZX3_Chick
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