Ok, my 2004 4.7 is doing something similar to this. It will idle down to about 500rpm and if you touch the gas it just dies. Also, sometimes it will run great but then the idle will start dropping and the engine acts like there is an electrical strain going on since the altimeter will climb to somewhere around 18-20v. I'm thinking TPS after reading this thread. Should I look at something else?
2004 Quad cab 2wd 4.7L
1998 Ram Reg Cab, 5.2 auto 2x4
Flowmasters to make her rumble...LOL