Yeah, try tightening them up first. Sometimes those rings can change shape due to heat, etc. whether the vehicle is old or newer. Two additional options:
1. Apply a very light coat of high temp sealer (like for header gaskets, etc.) to the rings and reinstall.
2. Have a muffler shop build you a flat flange that attaches diretly to the manifold eliminating the "rings".
3. On one truck in our family, it about drove us all nuts after a year, my dad pulled the rings out, made a copper gasket- it lasted for about 8 years and 160,000 miles on a work truck!