Genuinely mate there are pros and cons to each method. Long runners done properly will help a lot in some applications with midrange power and torque, these become a restriction at high rpm (sometimes) thats where short runners come in.

The principle is actually fairly similar to inlet manifolds, but instead of promoting the venturi effect you are aiming to promote cylinder scavenging. Generally short inlet manifold runners will help produce good power at high rpm, long runners due to the venturi effect will help produce good power lower down, the runner length and bore diameter can be designed to suit a specific power band. Variable inlet manifolds exist to help widen this band, the need to do this is some what negated by having a whopping big leaf blower on the front , so you start looking at equal distribution before you look at runner length i guess.

So a good manifold, exhaust or inlet will be designed for s specific application. If Gus's manifold was for more torque lower in the rev range it will be pretty long (hence being at the back of the block)...

This all works great in a N/A engine, im not all that sure if the same principles (exhaust wise) exist for a turbo engine due to the bigger back pressure present in the manifold.

Inlet manifold wise, often if the throttle body is not in the centre of the manifold the plenum will be tapered away from the opening, this is meant to maintain or increase gas velocity along the plenum hoping to achieve equal distribution of air, again i don't know but im pretty sure some manifold deliberately set the throttle body at an angle to try and achieve the same thing.

Its all got to be thought through, there are some pretty basic equations that can be done, and some fairly complex ones to determine the dimensions of either manifold.

Rob,