
http://www.fnsweet.com/garage/cai/index.shtml
Cold air inductions are trendy. However, on a 4.6L engine they net you no measurable power gains. They attempt to isolate the air filter area from the hot engine bay. A good start would be plugging all the coolant passages that heat the throttle as well as the intake manifolds. The heated manifold (like every other car out there) is why cold air intakes don't make diddly for difference - because the intake manifolds are heated! This is also why you can feel the difference when your engine is cold - because the intake manifolds are still cold also! The only problem with this is you can’t do it to 4.6L cars.
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Another problem is that there is now a bend before the MAF, which causes calibration issues that can lead to bucking, stuttering and early pegging of the MAF. What’s more is the chrome people use. Chrome gets hot and heat is the enemy of HP so you’re actually making your car slower by adding that “bling” item.
However, there IS a solution. A company called JLT has released a kit with some amazing gains to be had. The Cobras are choked from the factory stock and can gain HP from a CAI/RAI. The GT can gain a few ponies as well, however it is not nearly as significant. JLT’s gains have been proven on the market and if you’re looking for a CAI or RAI, I would look no further than JLT. They are the cheapest and have best product out there.