I removed my cat and now I want to remove my muffler and I have some questions for people that have already done this. Will I loose my bottom end power with the loss of back pressure? How loud will the exhaust be after removing the muffler with the cat? Can I use a programmer with the tunes already installed or do I need to get a custom tune? Will this lower my MPG?

 

Yes, but not very noticeable to most.

Louder at slower speeds, not much different at highway speeds.

Custom tunes are the ONLY tunes to ever use in a 6.0.

No significant change to MPG.

 

IMHO and experience,
Save your muffler or be ready to replace with a good flow thru like the walker BTM...

The drone and straight pipe was too loud for me and mine, but your results may vary

the link in my signature is with the walker btm muffling it !

 

When it comes to exhaust noise, there is a difference between pickups and Excursions.

More droning is heard in the Excursions because the interior covers the entire length of the exhaust system.

 

I dont hear it in mine either except maybe a little between 55 and 60 mph, other than that I dont even notice they are both gone until I get on it. Experienced no loss or gain in fuel mileage and the same goes for the bottom end power, no loss or gain.

 

here is a youtube video of a 6.0 with a straight pipe,

YouTube - 6.0 powerstroke straight pipe, beautiful sound

my truck sounds the same way and I just have a 4" straight piped, cat and muffler delete with a 5'' tip

 

You will loose some low end but it is unnoticeable. This will not lower your mpg. not sure on the tunes.

 

I pull a 12000 lb 5th wheel so I guess I better be prepared to add a muffler later. I will do the delete pipe and if it is too loud I will add a muffler.