I have an N14 SSS pulsar with aftermarket extractors(Unknown). The mounting is the same as stock but am having trouble finding the gasket that goes between the extractor and down pipe. Seen on another forum that it's common for aftermarket extractors that merge 4-2 to fail. Not sure of the condition of the gasket but need help if i should make the gasket and use sealant or try and repair the old. If someone knows where to get that gasket that would be much appreciated.
Take to an exhaust shop and see if they have a gasket that fits. Aftermarket headers will always just have a flat flange designed for a flat gasket, similar to the subaru one you linked but usually they're thicker than just a single metal crush gasket like that subaru one to account for 'lack of flatness' in the flanges.