I was wondering if removing the muffler will improve mileage?
Would it be safe to remove the muffler without continuing the pipe all the way to test it? Ive tightened the turbo boots, looked for fuel leaks, trying to drive conservatively bla bla bla still 12-13 mpg. Any Ideas?

 

If you wear ear plugs maybe, That diesel sounds so good straight piped you'll tend to stick your foot into it a little further. I would get a short piece of flex instead of stopping it just before the muffler for the test.

 

I've seen some people post about a 1 mpg gain, I don't know myself since I tend to have a heavy foot and I'm addicted to the turbo whistle.

 

I did that very same thing last year before I put the 4" system on and did not notice an improvment in mpg. Just more noise or music as some would say.