4x4 inlet have a better air flow if you use a 4x4 inlet you will need a 4x4 fuel rail as the fixings are in different places to the 2wd and you will need a 4x4 fuel reg as this is different as well 2wd has a bracket and a short piece of pipe the brackets are normally missing the 4x4 fuel reg bolts direct to the fuel rail your better using a 14mm spacer as its a straight fit then as you just bolt your fuel rail from the other side of the lugs with a 10mm spacer you will have to make or by some spacers for the fixing of your fuel rail and if you do space your inlet manifold your brace to the engine mount from the inlet will no longer fit without modification its not essential and you can run without it hope this helps