I was wondering if there is anything else special I had to do to change my turbo from a T3 to a T3/T4? Thanks in advance for your answers... I know they are the same bolt pattern but I was curious what I had to do...I have an external wastegate..

 

You'll have to redo some of your charge piping. The compressor discharge is going to be larger so you need larger piping. The compresser inlet is also going to be larger, so you will need to re-do your filter setup.