High Idle issue 98 ranger vin - U
 

I have a 98 ranger, 2wd, v6 3 ltr, Vin -U. I've replaced the thermostat, egr, ecg, 2 o2 censers and some fuses. The only check engine code coming up is P0401.

My exhaust does smell rotten but I have several catalytic converters. The code doesn't narrow it down for me. Is there any other, less expensive suggestions out there? I'm burning too much fuel idling. I used to get 330 miles a full tank and now it's less than 300 miles. I also replaced the water pump and flushed the system out.

I am open to all suggestions please. The truck is in great shape other then that one issue.

Thanks guys.