Short pause for clarification....
"Cold air intake" can have several meanings, and it's easy for new builders to get confused.
Without question, we always want to supply
outside air to the engine, rather than the very hot air from inside the cowl. The HP difference is significant. In general, there are two Vans-supplied methods to bring in outside air, the vertical induction airbox, and the horizontal induction snorkel. There are also lots of builder and vendor variations, most of which claim the benefit of "ram air". A well sealed outside air source can indeed be configured to convert some dynamic pressure to increased static pressure, i.e. raise manifold pressure at higher speeds.
The Vans horizontal induction snorkel does a pretty good job of dynamic pressure recovery, as it feeds directly from the left cooling air intake. It is also easy to live with long term, as it has proven to be very durable, and doesn't impact cowl removal or installation.
Kevin Horton photo:
The standard Vans vertical induction airbox has shown some maintenance issues, and can complicate cowl installation. However, there are thousands of them out there, and with a little care they work fine.
Romeo Lima photo:
Cold air
engine manifolds are a separate subject. The supposed goal is to separate the heat of the oil sump from the intake tract, thus providing cooler air to the cylinder. A lot of us consider significant air heating to be unlikely, and discount that aspect. The real benefit (
when and if it is shown to exist on a dyno) is more likely based in slightly increased mass airflow, and with some manifolds, the ability to mount a larger throttle body.
This is a Superior "cold air" intake and sump...
...and a Sky Dynamics "cold air" intake and sump:
The new oil sump may have its own advantages, like better oil pickup or inverted plumbing. That can make the intake manifold replacement worth the trouble even if it doesn't add anything.
We now return you to your regular programming...