either brent or seth at brenspeed told me that the stock cats that ford puts on the mustangs are pretty high flow and it would be almost pointless (save for 3-5 hp) to put on aftermarket high-flows...

 

running lt headers with xpipe with high flow cats will give you the check engine light well it did for me. I tuned it and it went away temporarily but it has come back like three time since then but you could just clear it with the tune.

 

Just a question on why you would add LT's and not get a tune? You wont see a big gain by just installing headers alone.

 

I'm wanting a deeper sound more right now than a Tune..

 

All a tune does for Long tubes is address the fact that the O2 sensors have been moved (or the rear O2s been removed completely) and update the switching speeds for the sensors. The power produced is all fom the headers, and none from the tune.

 

When I installed my equal length BBK headers and o/r x-pipe at the same time, I started up the car and let it run for about 15 or 20 minutes and got no codes or lights. Then I shut it off and used my tuner for the first time. Never saw a light or a code.

 

Depends on the year. I believe '07 and up the mils wont work. I have an '08 with an O/R H and tried using Mils and i still got the light. So i am getting a tuner now.

 

gauldurnit

 

I installed the Kooks long tubes, and catted X pipe from Brenspeed. I had no lights or any issues at all.

 

if you install LT's you will need a tune as your car will be running lean.