Per the first post in this thread: This turbo will not require you to send in your OEM core, you get to keep it. Why? Because we are recasting the factory turbo with bigger housings to fit bigger wheels, the CORRECT way to upgrade these turbos. The factory housings really limit what you can make for power on these cars, so we made sure to eliminate that restriction. This allows us to upgrade both the turbine wheel AND the compressor wheel, no clipping/cutting/modifying the stock wheel a TRUE turbine wheel upgrade without sacrificing spool.