Usually when you ask for help you should say "I've tested it using ****** way" not just I know it's not it. I honestly doubt the injectors are causing your hard cold starts. I just replaced 3 injectors in a students '99. It started like a champ at 29* outside temp with then bad.

Even with an injector that leaks down or sticks, if the cylinders are prewarmed ( glow plugs) the engine will fire off.

Recheck your diagnosis procedures and you might find something you missed before, instead of ****** rigging ****.