Thanks for your ideas shedracer, perhaps I'm not giving enough info here but I'm supprised nobody has made this stuff up before maybe everybody throws away the standard silencer, the factory team certainly don't use it.
What I'd like to know is if I remove the alloy sleeve will this give access to the baffles or is it just a cover, after sending some tie wire through the silencer I've worked out it's a straight through so my bits and pieces won't be able to damage the engine until the baffle pipe in the silencer burns out.The noise was found before the larger bore end cap was fitted and is still not. I'm thinking now if the rear end of the box is a single skin drilling a hole to let the bits pass out then getting somebody to weld up the hole.