Threaded Port could be for a Lambda Sensor? Used often in 4T exhausts, a 'plug-in' probe can assess mixture strength, fed back to the engine management on-board or externally, via lap-top. Just a guess, don't take this as read!

JHA cans, best bet is to get on OK!Shon / Jahoo Auctions.
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Rich
MC21 Track Bike / RS250 NF5 'Spencer', NX5 'Cadalora' & NXA 'Aoyama' / RS500 / Two Brothers Racing RC30