Ive been fighting an irritating header port leak for quite a while. And I finally decided enough was enough. My gaskets kept blowing out due to warped flanges. So, I went old school sprint car days on it. Now, as part of my exhaust leak fix, I had to do some welding, Because my mufflers had no support and just dangled about and eventually cracked along the bottom.
Thanks Dad!
I also discovered why they are so craaaaapppy.
Anyways, to fix your header leak, you need a tube of high temp RTV. The clear RTV sets faster but any color will work. You need to put a bead around your header port about 1/4 to 3/8ths inch thick. Put it on and let it sit. once the silicone is dry enough to touch with out it sticking, flatten out the bead a bit with your finger. Then let the silicone set for like 3 hours. Once it is hard, slap the headers back on and tighten the bolts. It should last the life of the headers. You will not need to re-tighten them later and they are reusable.
A bit thicker than this, I added some more after this picture.
I also snapped a couple of pictures of my actual full exhaust because I was bored.
This can help show the bends needed to go over and under the crossmember.
The bottom muffler on the last picture goes towards the transmission on my truck, and only slightly up/down. Both of my mufflers are equal length, parallel to eachother, parallel to the frame, and parallel to the ground.
After siliconing around the header ports, I have not leaked ANYTHING from the headers. And my truck doesnt backfire anywhere near as much. I have ZERO exhaust leaks now.