986 idles for a few seconds, then dies

[Jjay71]

Hey Guys
I'm new to the forum and to the boxster world.
I just purchased a 99 Boxster not running. I was told it was the ignition switch, and the switch was disassembled. I replaced the switch and the car starts but idles for a few seconds, then dies. If I try to give it gas it dies immediately. It seemed to be starving for fuel, so I replaced the fuel filter, pulled and cleaned the fuel injectors and reinstalled with new o rings and screens. I broke the fuel pressure regulator and replaced it. Fuel pressure at the fuel rail is about 57 psi.
I noticed oil in the intake, so I replaced the aos and cleaned the MAF sensor.
I replaced the spark plugs, so that takes care of fuel and spark. That leaves timing. Maybe the crankshaft position sensor? I hate to keep throwing parts at it, but so far everything has really been maintenance.
Any ideas would really be appreciated