I just put a flowmaster muffler on my 1998 F-250LD 5.4 V8. It took some time to research and make up my mind and then off to the muffler shop. Now it exits out in front of the rear tire with a 4 and 1/2 inch tip. This is as loud as you can go! The tip is a big help with the sound. There was no change in bottom end. when I have it for a few more weeks and I stay out of the gas peddle then I will see if it is better on gas. I did not reset the computer. Now when I get gas it makes me feel like I get my moneys worth. Thank you all for this web site.