The parallel fuel mod is reasonably common in the Subaru scene but there isn’t much aside from the kits you can buy.
This is the cheapest way of doing the mod and I’m doing it to my single turbo Subaru legacy bh5.
The intake manifold got a clean and paint before the fuel mods and I used some U.S spec 550 phase 2 side feed injectors and a roger Clark fuel pressure regulator and gauge.
That should help diagnose any future problems with the car.
