Update:
3D printed some injector adapters to backflow injectors. Same two proved bad even after backflow cleaning. Ordered two new injectors.
Injector filter baskets were gone. Only the brass and a tiny bit of plastic remained. Ordered and installed new stainless screens per other post on this site. Flow tested injectors again. No change.
Reassembled injector Teflon gaskets and gasket kit. Injectors are ready to be reinstalled, BUT…
I’m taking a detour and going to walnut blast the valves. The previous owner said they were done about 20k miles ago which looks to be true since I spent about 2 hours painstakingly cleaning all the old walnut media. 3D printed media blasting adapter. Cleaning valves next weekend…
Have a great week!