hi my name is mark, my 2001 silverado with a 4.8 l has me baffled big time new fuel pump, fuel filter, 57 psi at rail, new crank sensor, new camshaft sensor, new mass air flow sensor, new plugs and wires, have reset security just incase. truck cranks starts for a second very rough then dies have checked injector pulse its there have checked relay to ensure power and an active ground to ecm all there relay is working, have spark week but spart compression check 90 psi seems like a security issue but can not find that dam security box to remove it i know how if i can find it dont know where to go from here its got me baffled big time checked for vaccuum leaks none found no did not use smoke test old school the night this happened it was raining went to store came out got in truck started running like crap drove it home in like limp mode and has not run since cant seem to figure it out got me baffled here checked grounds already any help as to where to go would be great