How come some PSD's sound different than others. My brother in law has an excursion PSD 2002 model and i have a 2001. my engine noise, even at idle, is much louder than his and our motors are set up exactly the same (6637 mod, Tymar HPX, and Edge Evolution programmer). his sounds like it purrs and mine truly cackles. we both run .7 oz. per gallon of DK in every tank, etc... his is just much quieter. when i floor mine, it makes a great intermittent sucking sound (suck-suck-suck-suck-suck), however his makes a continual sucking sound (sssuuuuuuuuuuuuuuuuuuuuuuuuucccccccccckkkkkkkkkkk kkkkk). what am i missing here? Could it be the whole fuel return line thing? how much are the kits for those and does it help that much?

 

More than likely you are sucking in more air into your fuel, and your fuel pressure is lower. That will cause more cackle and injector knock. Some sponsors sell the in-tank/pre-pump mods (ITP, Diesel Innovations, etc) that will help take care of that air. You can also shim the fuel pressure regulator to bump your fuel pressure up. Ideally you want it around 65-70 psi.