Like the previous post said , a fuel pressure (leak down) test would most likely identify the problem. But there could be so many other reasons for your problem:
*Ignition system (cap, rotor, wires, spark plugs (only use OE, not any other make/type.)
*Cold start valve
* temperature sensor,
*Fuel pump, (2)
* Others less likely:
* Stretched timing chain
You really have two options:
1) Throw parts at it until you are lucky enough to replace the right one.
2) Have a good/solid diagnostic made by a knowledgable/competent pro.
In most cases, solution no.2 is less expensive.