Erratic idle on 1998 Dodge Ram 1500

I have a 1998 Dodge ram 1500 5.9l 4x4 108,000 mi I let the truck sit without much use over the past few months and I drove it the other day it would occasionally miss when the cruise was on. After that the truck reved its idle up and down when in parkon it's own. I knew something was up and figured I'd look at it tomorrow. So I went out and started it, started fine but when I touched the gas, it died. It wouldnt restart unless I put it to the floor and it would then run but if I took my foot off the gas it would die. If you let the truck sit a few hours and will start up but again once you touch the gas it will rev up and die. Check Engine light went on-OBD 2 code reader says 0505 idle fault. Doesnt help me a whole lot since I knew that from holding my foot on the gas pedal! :D Does this sound like an EGR (Which is supposedly not replaceable according to an auto parts place or is it TPS? Any inf would be great! This truck has had a full tune up dis cap, wires, rotor, plugs It seems the truck chugs a bit when cold idiling and smells rich, gas milage sucks 12mpg but, it is a Dodge!