High Idle and rough in lower rpms ???

[budget_crx]

I fired my Buick up a few minutes ago and it was idling a lot higher and a bit rougher than usual. Fuel pressure and vaccuum checked out ok and the CEL was NOT on. I drove it down the road and it seemed to drive as normal, up until about 50mph when it shifted into 4th. While cruising at this speed the car seemed to sputter and choke due to the low RPMS. When I came back and parked it, it continued to idle high. Any idea on what it could be and what should i check next?
TIA

 

[budget_crx]

my O2 readings are a constant 945 millivolts, with a a 1-5 millivolt jump everynow and then. Shouldn't there be alot more jumping between rich and lean?

 

[BlackMetal]

Yes the O2 reading should change and 945 is almost pegged out completely rich.

 

[WS6]

I'm gonna guess here. Either the MAF,TPS or O2 sensor(s) has given up.