I have a 2004 6.0 crew cab. I was having the shudder that I know a lot of people on here have had, and from the research I had done online I was contributing it to either EGR problems or injector problems. I cleaned the EGR, and it helped the truck in general (felt like it had some more power), but didn't stop (or help) the shudder. So I had a buddy of mine scan my truck, and it turns out that the #1 injector was acting up. I thought it might have just been sticking since it wasn't a constant problem it eased up as the truck warmed up. So I ordered 8 oz of the Rev-x, and sure enough my truck drives like a new truck again. No more injector sticking, idles a lot more smoothly, seems to have more power (seat of the pants wise). I can't say enough good about it, I just hope that it continues to run this well! I will most likely order some, and start adding 4 oz at every oil change.