It may be as Chepetech mentioned, grab a rubber mallet and give the muffler a good whack, maybe you will hear crap rattling, failing that, remove the muffler and take it for a drive ( the car, not the muffler), it's going to be loud.

 

Thanks man I will do, what you think of the clicky sound below?
It is in the SSV /TB area, been told could be vacuum but would expect this to be louder?



Thanks for your input