im in the process of doing a experiment about best fuel milege. i had a performance muffler on my 4 inch and i got about 13 MPG around town(alittle heavy foot), i just straight piped it and im going to see what im getting now. what do you guys think better or worse?

 

You should gain, if anything, but probably not enough to notice.

 

You will get worse with a straight pipe.....because subconsciously you will not be able to keep your foot out of it. Trust me. In terms of theory, I would think that you would get slightly better mileage but most of the reading I have done suggests otherwise (except for straight versus stock - stock sucks).