I think that I am right in saying that, the more modifications you do to your engine, the more each mod works with all and the end result is therefore much greater. However, ported heads, gas flowed plenums, balanced cranks, internals etc. will add upto more than your rangie is proberly worth! If you haven't already go for the easier and cheaper upgrades like the tubular manifolds, kenlowe fan, straight through air filter etc. There will be a big difference from these few, and they are alot cheaper. I have just moved my airflow meter so it now is facing the side of the bonnet with a k&n cone on the end and a vent in the side of the bonnet. Now the air travels straight to the plenum and I have to say that the throttle responce has improved and along with the tubular manifolds it is freer reving. These two mods work together quite well as it now takes in air with less restrictions and releases the gases with less restrictions. Although it would now benefit from an ecu remap to it is then set up for the mods.