I have been told that the Stock Air box is just fine for feeding air to the turbo. I wanted to know if a after Market Carbon Fiber Air box would increase performance? I have just added a K&N filter into my air box with an upgraded diverter valve for higher psi.  

there is no airbox better than the stock airbox. The Carbon "Carbonio", is purely cosmetic. it looks good and sounds better.  

I've been told the same thing about the stock box by a guy at audi.  I kinda agree with the other guy when he says it would be mostly cosmetic being carbon fiber, but if you go to evoms.com they have 2 intakes that are $10 price difference but I can't tell which is supposed to be better.  But can you really go wrong with an "upgraded" intake?  Your carbon fiber worth the dough?  

I just added the Carbonio intake to my audi and noticed the difference. I also have the GIAC software with the upgraded injectors dont know if that has anything to do with it...  

Dude, I cant believe the responses you have gotten!  Go to ModShak.com.  I can guarantee you a 10-15hp increase if you upgrade.  More air means better performance. PERIOD.  I have an 03 turbo 225 upgraded to a 3" downpipe for better airflow, a bailey aluminm divertor valve for better AIRFLOW, amd a 3" ModShak cold air intake.  While I have had my chip flashed by GIAC and most people under warranty will hesitate to do so, I am running over 300 hp with my upgrades.  Without the air upgrades I would be running 25-30 less!  

The ModShack VTDA/TTDA will NOT fit an A4.