Air Cleaner.

[tel76]

I have just removed all the paint from the air cleaner on my 280sl for repainting and would like some info: with regard to the top.
the air outlet for the top cover is 3inches diameter , inside this is a plastic insert that brings the diameter down to 2inches (it is made out of fibreglass resin and held in place with a 3/8ths dia: plug)
   Is this standard?
   What would be its function?
Several months ago George Des suggested that this car could have been converted to run on gas at some point,could this be part of the same system ?

[waqas]

I've never seen a plastic insert in the air cleaner pipe.

I suggest you put all this mystery information into one thread (and add to it as you discover more strangeness). Possibly even add some pictures. One day you (or someone) will be able to correctly  guess the true purpose based on all the clues...