99 Sierra turns over but wont start

5.4L V8 98K Mi. We have fuel pressure, and spark. But this truck has always intermittently sported a 'Security' light on the message center. Didnt seem to effect anything.
But last time this happened, we used a different key - and the problem went away (still had intermittent security lights tho).
Right now it just acts like it starts, but then sounds fuel starved and dies.
I used to like this truck.