Before ordering my aftermarket muffler does anyone know what the stock dia. pipe is that runs into the muffler? I would hate to have the wrong size muffler inlet and have to use a reducer. I think it is 3" but it maybe 2.5".

 

my 06 FX4 5.4L was 2.5". Ive seen 05s with larger pipe even with all else being the same.

 

It's 2.5-inches. You would be better off with a cat-back system than cutting out the muffler.