More help needed i am afraid

I did have a look on search and in faq for this one, but cant see anything!!?
Sooo, whilst removing my heater matrix today (horrid

) I was checking out the manifold and down pipe. I have gases coming up in to the engine bay when starting from cold which go once the engine is up to temp which I am assuming is the gasket, there is also a serious blow from the down pipe to centre pipe connection, the result of an awsome hash job by the cars previous owner taking it to ATS, is being held by 2 U clamps on either side of the joint and loads of sealant!!!
Said previous owner came round today to laugh at me trying to do the matrix and we were talking about the boge job and the manifold. He then decides to mention that the 'bloke' at ATS said the reason the joint was not sealing was because it was a 16v manifold, which is apparently shorter than the 8v (like mine) so the centre section is to short to connect up...
So is the 16v manifold shorter? will it fit on the 8v? I cant realy see there would be any difference bettween them... or am I being stupid??

Cheers