Prepping for paint, sealing air leaks

After spending the last week filling nicks with epoxy and sanding, I blew air into the stern drains to check for leaks - I noticed that the forward posts on BOTH hulls leak air through a tube that is in the middle of the foam blocks. It looks like it's supposed to be there - anyone know?

Last question - the previous owner must have added some sort of sealant where the deck meets the hull - I sanded it off to prep for painting and didn't notice any air leaks, but I'm guessing there are probably some small leaks that were tough to spot - should I be adding some sort of sealant to that seam?

Thanks

Yeah, the tubes are supposed to be there to vent the hulls.

If you've got any leaks around the pylons, you should seal them. Silicon sealant seems to do the trick.