Now, if your talking N/A 5.4’s gaining up to 60hp with exhaust I can not really comment on but I do find that extremely hard to believe that you could gain 60hp on a motor putting out approx. 240hp. That would be a 25% jump in hp.

On a Lightning there is no way you would ever gain 60hp by mounting any exhaust system. 10hp I could believe on a Lightning but that is a lot. On a Lightning there is absolutely no gain in hp with any type of intake system because the stock intake system and exhaust system on a Lightning is efficient up to around 450hp. At 450hp or so is when you would need to start modifying the intake and exhaust system to see any further gains.

However you do mention there are write-ups stating 5.4’s have gained up to 60hp with exhaust and tunes. Again it is the tune where you get the vast majority of hp gain but there is no tune that will give a 5.4 N/A or supercharged Lightning 60hp gain. I am talking a stock motor with no other modifications. If you put pulleys and a tune on a Lightning then you could indeed see 60hp gain but NOT by exhaust or intake a lone.

I mentioned in another post it would be interesting to know what a stock 4.6 GT motor requires for cfm and then what the stock intake is rated at. It would then be interesting to know what cfm would be required to support 400hp on the 4.6 GT motor. I would surmise that the stock intake is rated at least 20% higher then what is required to support the 300hp stock motor.

I very well could be wrong but with my years of experience of owning a Lightning and learning from experts such as JDM Engineering, Johnny Lightning, and others I just do not buy an intake system can gain 20hp or more by itself with no tune at all modifying anything else with the motor.