Cold start injector; fuel pressure; fuel pump; fuel filter; pressure regulator. I don't see this as an electrical/CPS type problem. Could a small part of the old hose found its way into the injector rail? Just a thought.
Good - Fast - Cheap: Pick any two.
E23 735i; E30 318i; E32 735iL (X 2 - 1 Alpine White and 1 Glacier Blue); E34 535i; E38 735iL; R50 Cooper; R55 Cooper Clubman.
E21 318i; E32 735iL; E34 535i; E38 730iL; E53 4.4i