Performance Diffusor Question!

So confused as to what the difference is when it comes to buying the M Performance Exhaust system for an M235i with or without the M Performance Diffusor. I found a good deal on the exhaust system, but it is meant for the M235i without the performance diffusor. I eventually want to put the performance diffusor on as well so don't want to run into trouble with installation.



Someone please explain!



Thank you!