After asking here for some ideas I eventually decided to make a central air filter using easily obtained items, the main component, the air filter I obtained from eBay.

The air filter has 3" dia. intake and outlet which I reduced to 2" by using the silicone reducing hose also purchased from eBay. The other materials were 1.2mm flat and 2" exhaust pipe.

Because I was concerned about air flow into a 90degree change of direction I widened the entry point in the exhaust pipe. The flexible hose is the same as the hose supplying the air to the heat exchangers from the fan housing.

I also increased the height of the inlet box to 110mm for better velocity into carbs. To facilitate better sound proofing I also covered the housings with 10mm sound proofing with foil backing then applied carbon fibre wrap to the housings and pipe.

The difference was way beyond my expectations. Sounds like a standard Beetle now. Can actually talk to each other and listen to music.

The assembly is held in place by brackets attached to rivnuts in the fan housing.

That is impressive as you said the intake noise is normally horrendous and a stereo is wasted unless you play the "poor people doof doof music" and just feel the vibrations.

Yep - impressive

We really need a like button........

Awesome!

Love the carbon wrap over it too!

well done Greg, looks great

sorry thought you were somebody else

Great job!!