Ok guys, My question is... I want to put a bigger exhaust on my f250 super duty 5.4L including the downpipe back and getting rid of my muffler, (which already talked to my local va inspector and said it was ok as long as I got the cat.) with exhaust being so expensive for my pocket im getting my local shop to fab me one up... Question is, Can I go up to a 4 inch. Only mods I got is a intake.

 

you will never need 4" exhaust. 2 1/2 to 3 is big enough. I'd replace the Y then 3" after the cat. Turn it out in front of the rear tires.

Y pipe: Y Pipe 2000 - 2004 for 5.4L / 6.8L/ Super Duty's » 5 Star Tuning

Y Pipe 1999 - 2000 for 5.4L / 6.8L/ RV / Super Duty's » 5 Star Tuning

 

ok thanks for the info.