Good news on the center caps.

I have always avoided cone filters as unless properly engineered, soak up the heat in the engine bay and therefore rob you of power. The Air Inlet temperatures rise unless properly shielded from the heat. Most folk believe they make the car feel faster which is the classis placebo effect of it making more induction noise. (It makes more noise so must be quicker).

If they were as good as the marketing hype make them out to be, automotive engineers would design them into the engine design. A great deal of design goes into the induction and the induction length is critical for an engine to be on tune.

Also, they are prone to sucking in water if you hit a large puddle which have been known to destroy an engine (water is incompressible and therefore hydraulics the combustion chamber).

If you do go down the route of an Induction Kit, I would avoid Pipercross like the plague as I have used one (on a previous car) and the build quality looked like somebody made it in their garden shed.