Exhaust leak,Between header n cat..

Hi everyone, I have a problem with my exhaust again. I recently purchased a new apexi noir exhuast and new magnaflow cat. I put it on and the flex area between the strup shorty header and magnaflow cat is leaking and its making my smooth ep3 sound like a ups delivery truck. Does anyone know what size donut gasket or whatever goes on the end a strup shorty header to a magnaflow cat? The gasket that came with the magnaflow cat does not fit and that is the same as the oem gasket which is too small .Please help, thank you:msmile:

Look for (maybe) an RSX Type-S or TSX gasket. The kid who's got my EP3 now had to use a TSX gasket to fix the leak between the JDM CTR-spec catback and Type-S cat I had on the car.

(different gasket location, I know, but it's a route worth checking)