Cwilli01

After I installed my mac off road h pipe I had a leak on the drivers side where the h pipe connects to the header.I loosened the pipe and retightened it a few different times and moved it around trying to get rid of the leak. Is there anything I can do to fix it? Not sure if any kind of silicone gasket maker will hold upto the pressure and heat. It's on the side that doesn't have a gasket. 01 GT.
Thanks