I just bought a 2006 F-150 supercrew with the 5.4 in it. The previous owner put a cold air intake and a dual exhaust on it. I have been reading other forums and I keep seeing people saying that you need to have a programmer with custom tunes if you have an intake. They keep saying that with the intake it will make it run lean and cause engine problems. I have never heard this before and was wondering what everyone else thought.
On earlier vehicles (2003 and prior) there is much less of a problem with running lean after switching to a cold air intake (CAI) because the Mass Airflow (MAF) Sensor is a complete unit and the cross sectional area where the sample tube is situated does not change when replacing the rest of the intake. In this situation, the values coming from the sensor are still accurate and the PCM will adapt well enough to prevent a lean condition.
On the 2004 and later F150, the MAF Sensor is what is commonly referred to as a "Slotted Type" sensor that is removed from the stock intake inserted into the replacement intake. Most CAI kits run a slightly larger diameter tube than stock which changes the cross sectional surface area where the sensor is located. A larger area at this point results in lower air velocity through the sampling tube of the MAF sensor which cause a lower output voltage form the sensor. The PCM calculates this lower voltage as less overall airflow into the engine and adjusts the fuel accordingly to try to maintain the target air fuel ratio (AFR), or in other words it injects less fuel. What results is a lean condition... sometimes grossly lean depending on the CAI.
Long Term and Short Term fuel trims can correct up to a point. You best bet though is to go with something that provides custom tuning to correct the overall lean condition this is most likely resulting form the intake.
BTW - Which intake do you have?
In response to power output, it's quite obvious you'll not achieve gains on a gasser that you will see on a diesel... not yet at least! However, on a 225 RWHP vehicle, 30-35 RWHP (or more!) gains are going to be noticeable. In fact, we just dyno tuned the new 2009 F-150 and got some pretty impressive results.
Here are the dyno plots (Click on the images to view full size):
Horsepower and Torque
Horsepower, Torque and AFR
As you can see, the biggest gains were not on the top end but in the midrange... which is where you really need it! Notice that the stock AFR curve does not allow any WOT enrichment until about 4500 RPM! And you wonder why the trucks are always so sluggish off the line.
The AFR stays right at 14.6:1 throughout most of the acceleration. Now add a Cold Air Intake and you can easily see where a problem could occur.
Hope this helps.