I have the dd3's and love them, I also have a comp box, stock turbo, original vp44, 4 inch exhaust, pacbrake mounted on the turbo and I do fine with EGT's, I can get it hot if I try and pull with the box on too high, so I usually just turn it off or put it on 1x3. I will load up a 36' flat bed and haul round bales all day and never worry. I have about 80,000 miles on with this setup the way it is. 155,000+ on the truck total.