i use the oring's , i coat them real good with a coper based high temp silicone and slip them on the flange. then i put silicone on the flange and in the pipe flange ,then i let dry to a tack .then i put the pipe and springs on and let fully dry for about 48 hrs . never Had any problems leaking even with a turbo, and it creates allot of back pressure in the pipe. just like ( bansh- eman ) stated silicone is the way to go