I have a 2007 that was originally a 427. This was a dud when I first bought it,so I decided to have it turned into a 460P from the Mack dealer. It helped but it was a bitch to shift bc of the egr. So I sent the ecm to Heavy Duty Diesel Tune to have the egr deleted and turned up 100 hp. The truck was so much easier to shift but my torque was flat, I liked the 460P Tune better. So then I replaced all my unit pumps and put stage 2 injectors from Rochester in. Wow! What a difference it blows some smoke and has instant power. Keep in mind you need to have someone program your unit pumps to the ecm so the truck will run smoother.