I am told that if you have an older style pellet cat that exhaust mods likely won't do much, but that any newer style honeycomb cat is essentially high flow and will work well with exhaust mods. I have a 1995 F150 supercab 300 I6. Problem is the change from pellet to honeycomb occured about this time (so I am told) and I wonder what I have. The tech at Flowmaster told me the honeycomb would be torpedo shaped, whereas the pellet style would be flat. Mine is somewhat flat as two pipes come into it and it is deminsioned about 1 inch larger than the dual pipe inlets which makes it about twice as wide as thick. After the cat there is something before the muffler--I think it is a resonator?

 

That other thing is a second cat

 

You do have 2 cats on your stock pickup, right now I have on a cat back exhaust which should be loud and cackle some when i let off but it has yet to do that, so what am I doing? Either A taking both cats off and putting a new O2 sensor in or B taking the pipe from my second cat to my glass pack out and then taking a rod and knocking the second cats guts out and then firing up my pickup and blowing the chunks out, then I will replace my pipe to my pack. Anyone done this?