I had oodles of P030x's and some O2 codes around 95,000 miles in the Graphite. Threw 12 plugs and wires at it, since it was time anyway. All codes GONE.

I'd measure the fuel pressure, I wish there was a way to measure it under load, but I think if the pressure is failing at all, you will see it on the gauge even when revving the engine when in Neutral. I'd then look for vacuum leaks, maybe clean the throttle body, perhaps even do that "Seafoam" thing with the gas.

If none of the above do it, I'd throw 12 plugs and wires at it. If the car had 100,000 miles on it, I'd do the plugs and wires first.