I just bought a 2000 F-150 4x4 with 5.4 ltr and autotrans and am thinkng about the following mods.

K&N Gen II FIPK
Gibson Headers
Gibson Dual Sport Exhaust

Can you guys tell me how much additional HP I should get with this setup and if it will give me better mileage if driven normally. Any other goodies you guys would recommend? Also the mfg web sites state I won't void any warranties. Is this true?

Thanks in advance

Roger