03 GT, Ive already got a Flowmaster A/T cat back and im a little worried that a Mac off-road H-pipe will make it to loud so I was gonna go with a Mac h-pipe with cats(hi-flow ) will I need mils for this or will my puter not see these cats as hi-flow? Cause I know with a off-road H you need the mils. cause there aint no cats. Thank you and Happy Holidays

 

I ALSo is going to get that MAC catted H pipe. I was told that Most people didnt need the MIL's for the catted version.....Let me know how much of a difference the sound is after its installed...I hope its louder than the stock H pipe with like a thousand cats

 

you may or may not need them. If your check engine light comes on afterward then you will.

 

You shouldn't need them, never seen a case where someone had to use them with cats before. Only O/R mid-pipes have this problem.
Bryan

 

I know of many mustangs that needed them with catted mid pipes.

as for how loud will it be its not to bad with flows and an off road pipe at all.

 

Yah, my setup was rediculously loud, but that was before the headers and with a nice little exhaust leak After the headers it's still loud, but doesn't wake the neighbors when i get home late anymore. O/R mid-pipes are gonna be reasonably loud for the most part, but too loud is all dependant on your definition.

 

wow, so headers quieted it down? Might need to look into those...

 

Thanks, i think this is the set up im goin with and just wait and see if i need mils

 

thats how ya do it. and long tubes shouldnt make it quieter it should be louder?

 

do either of you have headers?? the tone of the exhaust got much deeper, they are not long tubes, but it did get a little quieter, yes. It's hard to explain, but everything rattles more cuz of the deep tone, but it's definitly less audible.

 

not on this car i dont but on my other ones i have. long tubes make them louder, not sure how its makes your quieter? thats kinda weird.

 

I've heard that shorties typically make them a little quieter, whereas LT's will make them a bit louder. That is kinda weird though.