Im planning on putting on hi flow cats. Ive been told that the stock tubing size in my 97 expedition with a 5.4 is 2.5" I went to magnaflows website and looked to see what cat would fit. I came up with the 94005. It also says it is 2.25". I dont want to be stuck with two cats that are the wrong size. Can anyone help me out here?

 

get ones for 2.5"... thast what I have

 

if you plan on using a single pipe cat back then use 2.5" If your going true dual i'de go with 2.25". Thats what i have. Truck pulls extremely hard with my ford motorsport headers, high flow cats and dual flowmaster mufflers out the side. all piping is 2.25".

 

The cat size should be the exhaust pipes size.