That would probably be #2 and 4 you're referring to.
I restored a FI exhaust totally but it was years ago. And pickings were slim. The locals didn't have a clue...
Lots of places carry FI parts from the heater boxes out but good luck finding the manifold pieces to the heater boxes. There are two cast manifold assemblies on each side. It's the #2 and 4 cylinders that have the "reverse J-tube" type manifolds that feed into the other manifolds via a flanged joint. These smaller rear manifolds are the
2 into 1 collectors that connect to the heater boxes. And don't forget the always missing support brackets that bolt to the #2 and #4 flanges that support the entire system. You wouldn't believe how many FI engines have these parts rotted off which puts all the weight on the heater box flanges, which then eventually crack and leak. FI systems are EXTREMELY heavy. I bought those brackets from the dealer I recall.
Even JPgroup.dk which has an extensive catalog doesn't list these.
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I would try to hunt down used ones and bead-blast them. Good luck.
RT