IanE uses reed splitters when he tunes RS engines.
He says on his website that they give better mid / top end power, for NXA models.
It doesn't mention NX5, but expect would be the same type of benefit.
IanE is tuning my NXA engine in the New Year, so will discuss this with him and give some more feedback.
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Rich
MC21 Track Bike / RS250 NF5 'Spencer', NX5 'Cadalora' & NXA 'Aoyama' / RS500 / Two Brothers Racing RC30