The stock air box and filter for the 5.4L (without factoring any kind of forced induction) is more than adequate.

Running lean can also be caused by altering the geometry around the MAF (as well as a dirty MAF - such as oil from an oiled filter like K&N offers). The MAF is a thermal transfer device (more air across it means it cools faster) and in order to work properly it must know the cross-sectional area of the intake pipe. Some A/M intakes alter this geometry and thus screw up the MAF transfer function. A custom tune can fix this issue, but it requires extensive testing with a lot of vehicles or a dyno run with a wide-band O2 sensor.

If you search for "Gotts mod", you will see a simple and inexpensive (less than $10) way to reduce the restriction at the fender well. This is truly the only place you need to worry about. In fact, for the 09+ even this restriction was eliminated.

Any exhaust mods would have to include headers to add any gains. Cat-back changes on these newer trucks simply enhance the butt dyno sensitivity (louder must be better).

 

So I bought an 05 F150 King Ranch Crew Cab with the 5.4L V8 last October. I've had the truck more than a year now and I'm ready to step into the world of mods for the first time. The truck had a cat back 3.5" dual exaust installed when i bought it, I cut the muffler off the day after. I lucked into a free SCT X2 and was going to pair some tunes with a CAI. But if i understand you correctly youre saying I would be better off with the tunes and the GOTTS mod? What if I gutted out the cats? I live at 7000ft of elevation does this make a differece? Greatly appreciate any help.

 

Unless you plan on forced induction, the gotts mod will do everything you need.

Call Mike Butler at 5Startuning.com or you can PM him (fordmdb) about gutting the cats and custom tunes. And yes, 7000' elevation definitely makes a difference in your custom tunes.

 

Before my stroker rebuild for my 01 Bullitt I was getting 275HP and 300ft lbs to the ground with a CAI, headers, cat back (well...there's no cats), and a Brenspeed tune. Sure, now it's more like 320HP and 340 ft lbs but hey, it scares the camaro ss's from stoplight to stoplight.

 

Tylus, I have had an Airaid CAI on my 04 FX4 since new and have NEVER thrown a code, and it is a California truck...question answered...!!!

 

There are plenty of documented cases on the Internet. I will say that the DTC may or may not show up. That doesn't mean you aren't running lean, especially at WOT.

Ever used a wideband 02 sensor and measured your AFR?

Regardless, all your example means is you should have bought a lottery ticket 'cause you've been really lucky.

 

So after three days of research and some careful consideration...
I have confirmed through SCT that my SCTX2 will work fine on my truck, and so I have decided to pair it with an S&B CAI.

I picked this CAI because the air box seals completley and pulls cold air through the stock hole in the fender as well as from behind the headlight. Also some of my research showed that the problem alot of CAI's have that throw codes are from oiled filters sometimes cause problems with the MAS. This kit uses a dry disposable filter that is interchangable so I can go with the cotton filter later if I wish.

This paired with some custom tunes for my SCT X2 and my existing cat back exaust (sans muffler of course) should be a nice upgrade.

Thanks for the tips everyone!

 

You can purchase the S&B and the tunes through 5 Star Tuning. Just FYI.

 

Already bought the S&B (had a credit). Need to get in touch with 5 Star. Do they write the best custom tunes in your opinion? Will they factor in elevation?

 

I cannot speak towards elevation as I'm pretty much at sea level. His tunes work nicely in my truck. PHP writes great tunes also, but their wait time is much longer than 5 Star's.

Go to SCTs site and see if there is a local shop that is familiar with truck tunes. That might be your best bet with your elevation needs.