Maximum Exhaust Flow

for maximum flow, gut'em all. But if you're only going to get 2 of them, make them the uppers, since they are the first to contact the exhaust, they would cause the most influence on the flow of the exhaust.

I’m telling you this from personal experience DONT DO IT
If you are planning in gutting your cats just gut your precats. Don’t gut your secondary cats (the big ones). I DID
My Experience with all four gutted cats.
I was happy with my just precatted cats and one day for some reason I decided to gut the secondary cats. So I went and did it (it was a hella a freaking hard job it took me 3 hours per cat)
I went and got the pipe back and damm I was impressed it sounded like a V8!!.
At startup sounded sweet I went and revved it up many times and dammmm it was nicer (from driver’s seat).
The next day I called my V8 buddy and he couldn’t believe the sound he gave me compliments too. (I felt great).
A week later I tell my buddy to drive my car and I will drive his. He was cool no problem. (Then I noticed!) When I was following him it’s sounded nice! BUT when I stoood or drove next to him it sounded like crap It sounded like loose nails rattling in an empty can. Especially when he stepped on it.
Sounded great when it was parked and I was revving it! WTF!!
I took the pipe out and inspected it just incase I might had left some pieces
But the pipe was clean.
I got so frustrated that I went and traded in my 6er for a 02 GT.
Now I am happy as hell.
Just for your info I had a 2000 v6 with pullies,k&n intake,diablo chip,4.10's, dual flowmasters 40series.
Don’t get me wrong when I traded my 6er it was like I had lost a son. But I felt better when I drove PROJECT ELEANOR (MY NEW V8) home.
Hope this can help you out; if I was you just gut your pre cats. And be over it.
You will have no power gains or losses with no cats or cats on.
I didn’t notice
just in case you want to know how my car sounded with just the first pair of cats gutted.
http://members.cox.net/newhome_4u/Mustang.wmv

i listened to the clip, but i heard popping!? was that from you flowmasters or from the gutted cats? i have dual MAC exhaust on mine, its just as loud, and it doesnt have the popping sound, or not that ive noticed...?

Yeap that popping is the flowmaster signature

So that clip was just the cats closest to your headers gutted right.

Hey dmarco_4u, do you think that you would still pass emmissions with just the pre cats gutted?? One more question, did you get a check engine light after gutting the pre cats?

For alukigraves85
Yeap those are the first pair of cats, closest to the headers.

For Lay It
You will pass emmisions with just your precats gutted.
When i gutted the first pair of cats. I drove it like that for a whole month and no check engine light came on. Once i gutted my other pair of cats (secondary main) my check engine light came on the very next day, so i went to my best friend EBAY and got me a pair of mil elliminators for 40 bucks. after i plugged in the mil's my check engine light when away after i drove in the stang for 5 minutes.