96 mustang GT 4.6L - no start

96 Mustang GT: Was running fine. Parked for 2 hours. Now cranks but NO START. Occasional "pop" as if trying.

Had leaky fuel pressure regulator - replaced. Replaced Crank and Cam sensors. HAVE spark at all plugs and fuel at fuel rail (pressure = ~38 psi). Injectors ARE firing (checked with noid light). Theft light turns off after 3 sec.

What am I missing? Any ideas appreciated.

Thanks.
Charlie H