Exhaust leak at cylinder head

Hi all,

I hope this is an easy one. I recently installed a new exhaust and i think one of the pipes has not sealed properly. I think the tappety cylinder head noise is excessive. I did use the correct crush gaskets and i did torque it to spec. 

Has anyone used exhaust sealant along with the gaskets? I don't think that it is supposed to be necessary but it may be a solution

I just used the gaskets, and it's been fine. Have you rechecked the torque in case they've worked loose?

I did recheck it and it made no difference. 13nm seems like very little tension but thats what the book says