Well, H&S Performance's XRT is one of the most reliable, and code-free units on the market for DPF and EGR removal.
I have had 0 problems with mine, and love it! The power is unreal, yet very manageable to drive everyday.
I've been helping them test their 175hp tune, and let me tell you...it is a true monster...and adding power and modding your truck can be very addicting! LOL
I would honestly suggest starting off with the XRT...When I bought my stuff...I purchased everything all at once, and installed everything at one time.
I installed H&S complete EGR & cooler delete kit, 5" Turbo-Back straight-pipe (TBE), AFE Mega-Cannon II cold-air-intake (CAI), and my H&S XRT tuner on 120 (highest tune available at that time), and my Quadzilla Boost Fooler.
I have never looked back, and never gotten the fuel-mileage I get now! I'm getting 15 or so around town and between 18-21 highway!
Which, for a huge truck like mine is pretty impressive. I jumped over 5 MPG's in town, and 5+ on the highway!
I would suggest just starting off with this setup, b/c you will eventually work your way into it, like alot of folks that I've seen on here do.
I've seen alot of folks spend thousands and thousands on stuff, that they now store in a box in their garage b/c they don't use it, or something better came out...
I'm not trying to deter you away from your choice, just trying to give you a bit of advice where I've seen many others make mistakes.
If you choose to still go between your originals go with the Hypertech MaxxEnergy AND Diablo-Sport Extreme Power Puck (same thing as MP-8, but cheaper and just as good a product).