Security system, air, fuel, spark, compression.
I assume you don't have a security light on? (Yellow pad lock symbol in the instrument cluster.) If you're really getting spark, then this probably isn't the issue.
We'll assume you're getting air (as opposed to having a rag stuffed in the intake somewhere).
Did you properly reconnect the injector harness (to the injectors and to the main harness)? Check fuses & relays?
Last thing would be to perform a compression test. The numbers will be off since the engine is cold, but it's an easy test and may reveal the problem.
Blue-ish 2006 2.4, Werks stage 1 turbo, Borla cat-back, DDM braces, Spec aluminum flywheel, Spec stage 2 clutch, Werks aluminum radiator, some gauges, RKSport hood, Morimoto FX-Rs, GReddy Profec, Norm's fenders
'07 GXP, RPM Stage 2, Solocatless downpipe, TCE Wilwood 6 piston front brakes, 4-piston rears , Stainless brake lines, slotted/drilled rotors, BC Racing BR coilovers, Performance Autowerks intercooler, DDMWorks CAI, charge pipes and braces