I have a S4 NA and I was wondering if when porting the intermediate housing if you remove the fuel diffuser/ atomizer thing that is right below the the fuel injectors?

 

Porting the engine has nothing to do with whether or not yoyu leave them in. They are probably very brittle so good luck getting them out without breaking them. I do take them out when I do engine work but I also put them back in when I put the engine back together. They actually don't hurt top end power. They don't restrict airflow near as much as they would appear to. They do help the fuel enter the engine at low rpm's which aids in low speed power and starting. If you take them out when you port it just remember to put them back in. You can leave them out entirely and the car will run fine though but any benefit they give is now gone.