Here's my friends 6.0 Excursion with 4in exhaust w/ muffler. Its a cold start but gives u a idea

 

I did an MBRP 3.5 inch down tube into a 4 inch Dynomax cat back (yes, I could have saved money and headache by buying a 4 inch turbo back system from the start). Anyway, no cat, no resonator, and the straight through muffler was very liveable inside. In fact, with the windows up, it isn't too bad now that I dumped the muffler too. However, it is a loud throaty exhaust when you put your foot in it!

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Be-lay my last, I completely missed that 7.3 part. The only person I know with a modified exhaust on a 7.3 is a 4 inch down tube, 5 inch exhaust, no muffler, no cat. Its pretty obnoxious on the throttle, but a muffler could solve that. It's an aluminized kit from Summit Racing Equipment.

 

I just installed a 4" Diamond Eyes turbo back system with cat delete. It took over 4 hours and most of that time was trying to get the down pipe from the turbo removed. There was a lift point bolted to the back passenger side of the block that was in the way for a easy removal. I finally had to remove the trans dip stick and remove all the added heat shield from the pipe. I had just enough room to get it free.

I love the sound of the exhaust. I can hear the turbo winding up when I accelerate. The inside sound is barely noticeable when cruising down the road. I paid 265.00 for the kit plus 50 bucks for the cat delete. It is a nice kit, but the lower cost comes with some design shortages IMO.