I soundproofed my 2001 4wd quad cab Diesel today. I used 3# to the sq. ft. lead sheeting. put it on the valve cover,under all the the floor carpet,then used some foam pieces to cover all the open spots on the firewall including around the steering shaft under the hood and under the dash,on the panel behind the back seat,and in the rear corners of the cab. Also put a strip of foam on the cowl right behind the rubber seal so the hood sits on it,also put foam down between the front of the doors and fender. It is a completly different truck, the only noise now is the injection pump and even that is very muffled,i could eliminate the injection pump sound with some lead sheeting also but i dont know if i dare do it,maybe the pump would run too warm although there is a lot of fuel being circulating through the system to keep it cool, i might do it and keep a close eye on it to see how warm it gets. I may put a thermometer on the pump and see what it runs at when its hot outside then cover it and see if it does run hotter. I didnt take any db readings before or after but i know i cut the noise down by at least half , probably a lot more according to my wife, and she knows.