Haven't a clue unfortunately. Being a carby engine, maybe something to do with the antipollution system, they're certainly complex with hoses going everywhere compared to the FI, and they were bad enough back then. Don't recall anything like that on the A20A carby engines. It has a vacuum hose (hose #31), what else is it connected to? Is there a diagram sticker on the underside of the bonnet? Probably need a translator to read it if there is, bound to be in Japanese.