It will start if you disco the injectors? That means there's fuel in the intake. Leaking injector is my guess. It will start cold because the mixture is marginally ok with a cold engine, but way too rich for a hot motor. Does it start immediately when cold, or do you have to crank a while?

The Westphalia noted above had a similar problem. The crusty hose was leaking, giving the pressure regulator a false high signal, thus causing an overinjection of fuel (the pressure diff between fuel and the intake mani vacuum is too high because of the faulty pressure regulation).

The ecu has to assume a constant fuel pressure diff over mani pressure, otherwise the amount of fuel injected is wrong, because all the ecu controls is the number of mseconds the injector is open.