As a former 145 owner continually doused with exhaust, I strongly recommend that you fix it. As George notes, there is a gasket in there. Don't believe the parts guys if they tell you it doesn't have one (I was told that when I was 19 yrs old with my leaky 145).

My guess is that probably have a failed gasket in there, It's not uncommon for the nuts to loosen up and the heat to burn out the side of the gasket.

If your nuts are frozen up and you happen to break them, I suggest taking it to a machine shop and getting the surface planned smooth and have new bolts put in. You're lucky in that a 140, unlike a 122, has some spare space around the flange so that you can get some leverage to loosen and tighten the nuts. Be careful, use lots of Pblaster and don't be shocked if your bolts snap off. I've had it happen several times. All that heat and road water is not very kind to the studs.

Good luck.