i have an 03 expedition with the 4.6 in it and Im thinking about swaping my intake manifold for some performance stuff. BUT the parts im looking at right now are an upper (or plenum) , and a lower manifold...the upper costs only a couple hundred but the lower is wayyy more expensive, Im considering just doing the upper manifold and keaving the lower alone but first I want to know if I would be wasting my money by only doing the upper and not the lower. Anybody?

 

As far as I know To take advantage of it you would need a throttle body & CIA. I put the 75 MM TB on mine and ported my stocker upper to take advantage of it.