Ok, I've been searching and reading a lot about different headers. I really want to upgrade my stock manifold to a set of long tubes. I have an 06 5.4 xlt 4x4, my question is this. Is there a difference between headers when it comes to 2wd and 4x4? I found a local company (American Racing) that makes headers for an 05-09 2wd?

 

With regards to the actual headers there is no difference in 2wd verses 4wd. The difference is in regards to mid-pipe set up. That is all.

 

With long tubes you'll need a custom tune

 

Does it have something to do with the transfer case being in the way?

 

I don't think I'd say NEED a custom tune. Want, yes. There will be no drive ability issues with a stock tune and headers. You will also see performance gains with headers and a stock tune.

However to take full advantage of the available performance you would want a custom tune and better exhaust behind your headers.

 

Yes.

 

That's what I figured

 

Actually most people "need" a custom tune with headers.To explain why heres a quote from the book "EEC IV Inner Workings," by tmoss (2002), "The EEC has a timing table used to time the sampling of the O2 sensors to coincide with the arrival of the latest cylinder exhaust pulse from each bank. Moving the HEGO sensor further away (or closer for that matter) may result in an ill-timed sample, which could also cause improper air/fuel mixtures to occur due to the O2 sensor not sampling when the pulse passes the sensor. One way to compensate for the additional time needed due to adding length in the Long tube headers is to change the timing table". This is done with a custom tune.

 

And longtubes lean out the afr a little too

 

So are you saying that with most, if not all, LTH the o2 sensors are necessarily farther down the line? Meaning the primaries are longer then the original o2 location?

So it is not the addition of the headers necessitating a custom tune but the change in o2 location?

I also note that it says COULD and not will. Has this theory been tested and shown to result in incorrect mixtures? I don't doubt it as the theory is plausible, I just wonder if it has been proven.