Could have saved myself some hassle if I had bought this.
I ended up getting a Magnaflow thats the one listed for Yukon Denalis. Turns out their website lists the wrong system for the regular sized Denali. Basically they have their XL version listed for the regular size. I put it on minus the center extension and the tailpipe hangs off the rear bumper 8"!!! Magnaflow isnt even aware of this. Im waiting to hear what they think the solution should be but they have already told me that they will not send the Escalade one as a replacement "because it wasnt built for the Denali".