well i got my combo today from the GB, and i bolted the dp and header together ( i was bored ) and i made sure they were tight and it seems like in the middle of the flange(?) it isnt air tight, is it supposed to be like this? it is very tight on both ends

 

Did you put the gasket in between the flanges

 

Sometimes it can look like that actually, dont ask me why cuz i dont know. But i work as a mechanic at a dealer and i have questioned myself many times after doing exhausts that dont seem to be tight. I say fire it up and see if it leaks, almost guarantee it doesnt