I honestly do not see how moving the throttle body away from the intake would increase fuel economy.

 

They are machined to make the incoming air swirl, which is supposed to allow the fuel and air to mix better and create a more efficient combustion. From what I understand, they've pretty much been disproved.

 

Little value if any. You'd be better off with a tuner or an exhaust component. If it netted a result of fuel economy Ford would have done it from the factory. The aftermarket has sold TB spacers for 20+ years for just about every application known to man.

I can't remember coming across any scientific studies and test that validate the benefits of TB marketing.

 

Stage 3 has one

 

A spacer also had the advantage of increasing the plenum size of the manifold. Again, this made more sense on a manifold that located the carb or TB in the centre of the manifold. But, I always thought this meant the person had the wrong manifold.

 

I've always been told that a bigger plenum was better for low end, and that a shorter one helped up top.