i am installing a merc 496 dts where a merc 350 mpi was i would like to know if the exhaust y pipe is the same small block and big block . also what is a transom harness for a dts motor what is it for ? do i need absolutly a ddt to program my dts or can i use a vessel view my engine is a 2009

should be same y pipe, but you should have a boot instaed of a bellows on the outside for more exhaust relife. And as far as i know you will need a mercury computer with g3 on it to set up your electronic shift and throttle. the transom harness is for digital trim, and rudder angle, stuff like that.