Malaguti phantom sounds like no exhaust

[lydanial]

It's a malaguti, as mentioned above, and it's taking a hell of a lot to start it... and when it does start it sounds like someone has nicked his exhaust.

The last time he rode it, it was raining and he said it rode quiet, it still pulls as well now as before hitting 55mph.

I checked the exhaust and it doesn't seem to be pushing enough gasses out of it, however, next to the exhaust headers on the left side of the engine is a big fat 'breather box?'? And more than half of the emissions are coming out of there, hence the loud 'no exhaust' sound. Well possibly not emissions (as I can't tell) but more 'exhaust' pressure is leaving that than the exhaust!

So I'm open to suggestions where to start, and would love to know what this rubber box is on the engine side?

Thank you very much.