Delete your dpf/cat and your egr system, this will definitely free up some more power and also bring your mileage up 2-3 mpg as well. Look into getting an aftermarket cold air intake and coldside intercooler pipe as well. You will need a tuner to run any of the deletes. I will list a few brands below for you too check out.
Exhaust(Downpipe back or Turbo back); MBRP, FLO Pro, AFE
Intake; S&B, AFE, No Limit Fab
Tuner:H&S (XRT Pro, Mini Maxx, Black Maxx), Spartan and SCT
Coldside Pipe; MBRP, No Limit Fab, Flo Pro
I have the Mini Maxx, MBRP exhaust and the S&B intake and couldnt be happier.
Read some of the stickies posted in the 6.4 section, they will tell you just about any other info you would need too know. I purchased my intake, tuner and exhaust from Performace Truck Products. Great company, great prices and fast shipping. If you have any questions ask away...Welcome to the Org