Every time I start it, check engine light comes on after 15 minutes?

My 89 chevy Cheyenne has been stalling on me lately. I replaced the plugs &
plug wires. It runs stronger but still has the same symptoms. Every day I drive
to work and around 10-12 miles away the "check engine light comes on.
Before I changed the plugs and wires it would do the same thing but run really
rough and eventually stall. Now it runs decent when the light comes on but
now and then it will run rough and/or stall. What is the next possible part to
look at? Fuel pump? Cap & rotor? Yesterday it stalled only a few miles away
and I have at least a half tank of gas. Note: if I pull over and turn it off for a
few minutes, It starts right up and the light won't come on for another 10
minutes??? You would think that if the light came on and it was warmed up
the light would come on when I restart it? So, tune-up unlikely??? More like
fuel pump pressure?? any thoughts?