WELL, I FINALLY FOUND IT...This has driven me crazy for over a year...Yesterday, I decided to take the time to find the vibration or else...I would have swore the vibration was coming from the area of the accelerator pedal..a bad bearing or something..After taking it all apart, lubing it, etc, to no avail..I went under the hood..I used a long screwdriver and pushed on the accelerator linkage under the Triton 5.4 L cover...the cover vibrated at low rpm..there is one screw on the passenger side that was barely loose, causing a short, quick, vibration, but only with it in drive...I tightened the screw only one turn and WALLA....NO VIBRATION...I know this may sound crazy, but I just can't handle vibrations....Now I can start the New Year off "rattle free"...Hope you all have a rattle free and Prosperous NEW YEAR also....