Car revs while coasting

Okay... when im going down the highway at speeds from 40+ and i put my 99 ford Taurus wagon into neutral the rpms will rise depending on my speeds...the faster i go the high the rpms rise.

Second problem car will shake when under a load at 30mph at 1800rpms

Can anyone help me with these problems? please email me at [email protected]

Sounds like something's wrong with the torque converter lockup. Is it an auto?

well thats what i thought but then i also thought it could be the cam position sensor... but when i unplug the air/idle control on the throttle body the rpms drop and act fine... and its a new air idle control and new throatle position sensor and new EGR Valve... i just really want to know why my rpms rise when i put my car in neutral and the rpms rise when over 40 MPH