I own a Dental Lab, and get all my car parts sent here first. I usually take apart any new turbo for many reasons. First, to remove burrs, bumps, and bubbles from casting, then I fill holes inside compressor cover where they poke thru from outside, while leaving room for the screw to hold on cover. I bellmouth the compressor outlet, and the back side of the wastegate hole. Look over turbo for anything funny. Sometimes you find a small flaw on a wheel, maybe a chip of metal ready to flake off. Then to the back side of turbine cover. I bellmouth the exit of the main turbine area just past the tip of the blades. You can only do 50% of the area around the turbine on big turbos because of the downpipe sealing surface is tight on the turbine exit. This helps allow a smoother transition from turbine to downpipe. Sometimes a lot of grinding is needed here!