From reading it's clear the 4x4 inlet manifold has advantages over the 2wd one. I heard the 2WD one is good for 350bhp max?

Can someone give me a brief run down on what the differences are, and what it takes to put a 4x4 inlet on a 2wd, I heard fuel rail, Reg and something else?

Also - what's all this about spacers, 10mm, 14mm? Can they be put on either manifold, what's their advantages?



Thanks in advance.