Piers Diesel Research HX35 turbo, is a modified Holset HX35 turbo that comes stock on most our trucks. You can read about it on piers site. -- In short he leaves the exhaust side stock, and on the compressor side installs a much larger pinwheel and machines the housing to match each individual pinwheel.
The result is an HX35 with a bigger efficiency map. Flows more air for lower EGT's and spools up really fast. You want one if you are towing, or BOMBing to the 350-400 hp range. Above that you need one of the HX40 variants.