Are you by chance talking about the Ford 6.0? If so ask around at http://www.ford-trucks.com/. Don't bother at thedieselstop.com, too much drama and know-it-all-ism. To try and answer you question. I don't think anyone has found a way to eliminate this "turbo cough". Its believed to be a backflow of air from the sudden change in the VGT vanes during a quick reduction in throttle. I'd like to see someone quantify this. Also, the manufacturers make these parts out of crap steel. With all the soot that accumulates in these parts and the moisture that accumulates in the soot and the acidity of the soot, these parts rust out rather quickly. Even a mediocre quality stainless would be much preferred. If I were to choose a small diesel to tune the heck out of, I'd look back a few generations before all the "modernization" happened and when stuff was simple and overbuilt.